I always have used my Draw knife bevel down so I can use the bevel for leverage to force the cutting edge up and out of a deep diving cut. .Flat side down you don't have the bevel to fulcrum the edge back up and out of a diving cut it will just stop the cut . flat side up lets you rock the knife on the bevel and have more control of the blades cutting angle. If it starts to do a diving cut you just twist the handles up as you pull back and pull it out of a dive my tool s are all razor sharp I use red metal polishing compound and leather .
this sounds just like the way experienced carpenter uses a sharp chisel for mortising.
amazingly enough i read in TBB where one of the masters uses a dull draw knife to remove sapwood. he explained how there was a difference in sound that the softer wood makes as the dull blade crushes the fibers rather than actually cutting them. he'd use that to get the majority of the softer wood down to the heart ring he was after, then used a scraper to remove the rest.
i gotta admidt... i never had much use for blades that weren't really sharp myself..... Kirk
