There's plenty to read about, and plenty to be confused about, in this business. I would follow the instinct that you get from watching the videos.
Personally, I tilt my bow when I shoot so the arrow is laying on the bow. At release the arrow tends to bend sideways, around the bow, more so than it tends to bend up/down. So I want the long lines of the rings of the shaft on the sides, resisting the deflection.
Most of my arrow flight problems are from the arrow wobbling side to side, not up and down, so there is a lot of energy in that direction.
When I spine the shafts I'm only interested in the deflection sideways, so I hang my weight in that direction. If I spin the shaft 180 I get the same reading, if I spin it 90 I'll get a different reading.