A buck grunt works if you see the king of the forest and he is not hot on a doe. Then he comes over to lay waste to the upstarts challenging his domain. Younger 2.5 - 3.5 year old bucks kind of respond like "Yea, don't need my ass kicked today." 
Now a doe grunt and done like a short plead. will lead them in like on a string. You can do that with your throat and hands. Like a high pitched cow mow. Google doe bleat. I killed an 8 this year, buck grunt and "Nope" then doe bleat and he came looking for love and died. Five point running a far scrape like and doe bleat and he was 15 yards in front of me and let him pass. Lots a 4's and spike with the same stupid look, trying to figure where the hot doe is. Doe bleats are where its at, unless you see the big daddy buck looking for a fight.
Now, if the boys are following a doe. no sense even grunting. If they are hot enough on her I think you can stand up in the stand, wave your arms and yell and the bucks wouldn't notice you. But then you'd scare off the doe they are chasing and in turn, move them with her.
I agree with you 100% when you are talking about all the big grunt tubes that are out there. I killed a 280lb brute of an ohio 8pt after hearing him and another buck chase a doe up one side of a draw and back down and up the other side for 10-15 minutes just out of sight. Those bucks were grunting evey 2-5 seconds, and they were not nearly as deep and loud as any of the traditional grunt tubes that are out there. The hot doe finally lost them and slipped down past my stand. That big 8 came walking and looking grunting every 3 seconds, and when he popped out around a huge boulder on that hillside at 30 yards, his grunts were soft, consistent, "clicky" grunts that I could still barely hear well.
Most of the times that I hear bucks grunt, it takes a second, and then I think "was that a grunt?" That has happened nearly every time I have heard grunting whlie hunting. I understand why loud tubes are needed when hunting Kansas and you are trying to get the attention of a big buck that is a ways away or in super windy conditions, but every time I have ever grunted with one of those big, deep tubes, the buck will whip his head in my direction (if he pays attention at all) then head off at a faster pace than he was originally moving. Either they think it is a deer that is going to beat them silly, or they don't think it sounds right. I think it might be more to do with it not sounding quite right, because think about how many times you see video of a hunter grunting at an out of range deer only for the deer to pause, look their way, and keep moving on...then finally, a snort wheeze turns them in their tracks, and they march in all bristled up right to the base of the tree. You telling me that those bucks were scared of the deep grunt but not scared of the snort wheeze? I dont think so. I think the grunt got their attention, much like a "Mehp" does when you stop them for a shot. The grunt did not sound exactly right, but they heard it and are looking to see what made the noise...then the snort wheeze, which actually does sound like a deer snort wheezing, makes them think there is a buck that needs to be dealt with or at least checked out.
I've only heard two bucks that grunted differently than the soft, short, clicky "was that a grunt" sound. One was a buck that was growling. It was from the same tree I killed that 8 out of, and about 100 yards up that same draw...and out of nowhere, I heard deer crashing and running. One was blowing like a doe that just got a whiff of hunter BO, and the other was growling like nothing I've ever heard. It was intense, and it went on for 5 minutes or more. I was tempted to get down and try to sneak up there on them, because I knew they were likey too engaged to notice me sneaking up there, but to be honest, I was a little freaked out and hesitatnt about getting near them on the ground. I wanted to KILL the buck, yet I was intimidated about approaching him...so I think about 99.9% of the bucks in that area were steering well clear of that situation. My dad was about 100 yards below me, and he could not believe it either. I told him it sounded like the buck was flat raping that doe and she was blowing and freaking out. Now that I have seen videos of locked bucks that were near death before getting their horns shot or cut off to free them, I'm convinced that what I heard was two bucks that crashed hard once and locked up and were trying to get separated. It was definitely not normal, as I've heard it once in my lifetime of hunting.
The other different grunt I heard, I was sitting in my stand as daylight broke, and I heard what I thought was a 4 wheeler or ATV that someone cranked maybe a mile or two away. The woods were ultra quiet, and it was like the put-put-put-put of a 4 wheeler exhaust if you just cranked it and did not give it gas. It went for a good 10-12 seconds and I literally thought "I didn't know there was a house in that direction...4 wheeler." Then it stopped, and I thought someone turned it off or it choked out. Then it cranked back up...and I thought, "that is one odd sounding 4 wheeler...is that a 4 wheeler? WTH is that? then off again. A couple of minutes later, I hear deer walking, and I hear it again, and this time I know it is a deer grunting, and again it is a long, fairly soft, continuous grunt that sounds like an ATV ehaust, but this time he ended it with a "rev up" with some authority at the end. I then saw the doe ears back sneaking thru trying to stay away from him, but not hauling ass. He finally stepped out at 30 yards looking for her, looked directly toward me standing broadside, and he was a solid 20+ inches inside, had an old, grey face, and droopy donky ears. This was in SC where big bucks are relatively small, but this guy at least had serious width and good mass (never saw tine length or number well), and he was THE MAN of those woods. Unfortunately, my great looking shot found solid shoulder bone, and the "CRACK" let me know I had blown it...and blown it I had.
So...to make a long story longer, out of 40+ years of serious deer hunting, I've heard exactly 2 bucks make sounds that can be made with 99% of the grunt tubes on the market today. One was either the biggest, baddest buck in Ohio, or was one of two locked up bucks; one was the largest, oldest deer any of us have ever seen on my buddy's 1200 acres of prime SC buck woods.
So why blow a call to mimic that? I won't anymore. I'll take a regular grunt tube in to mimic that second SC buck when rut is kicking in OH or somewhere where the rut is defined and big bucks are there, otherwise, I won't blow one. I will use those little soft-sounding "clicky" tubes Raglin uses (Ill post the name of the things when I dig one out of my gear bag), because they do actually sound just like every one of the 50+ different bucks I've heard grunting while hunting. I only used them for a couple of years a long time ago, but I actually caused deer, albiet small bucks, to completely change their course and come to me with those tubes, so I know they attract, and I know they don't intimidate or sound "off" to the deer. Unfortunately, I lost them at a time when there was no internet shopping and searching, and I did not know what they were called. I also fell into the trap of buying calls that are meant to attract hunters more than deer, all of which I have used for 20 years now with little to no success. I'm glad I googled "roger raglin deer calls" and eventually found, and was able to purchase them again, and I'm looking forward to putting this theory of mine thru some serious testing next fall.
So, I think grunts can work more than they are currently working for people...if they just sound more like what real deer do. Deer aren't hollering across 20 acres at other deer...they usually grunt softly to communicate with deer that are near them...us trying to call at and make a deer hear us that is 100 yards away isn't realistic.
Thats where my head is on this subject at this time FWIW.
