Tune the way you guys want to tune, that is your deal. Just please don't be telling people that bareshafting tells them centershot. Or at least it doesn't tell them centershot when it is way off.
I dont recall anyone saying that ("bareshafting tells centershot") but I'll play along.
Bare shaft tuning first and foremost is a tuning process to find the perfect spined arrows!!
I , along with many others , also take it a step further to achieve the best arrow flight possible for hunting purposes.
Here is how I check my center shot. I shot an arrow at 5,10...30 yards (discard all bad arrows and shoot over). The arrows can do 5 things. Fall in a perfect straight vertical line (perfect centershot). Make a C shape which means the arrow rest is too far out. Make a Backwards C which means the arrow rest that is too far in. Or make line from high right to low left or vs versus. These lines mean the spine is out on the bow
Guess what you just described?

Do that same test with bare shafts and let us know the results. When bareshafting I do the "backup method". I think your just misunderstanding what we're trying to say.
When everything is set perfect , along with perfect spined arrows , my bareshafts will impact
exactly like my fletched shafts and they all impact straight as you described.
I've done the line check (draw straight line) method I think your refering to and when I've tried it after my bareshafting process it was always perfect.
I'm not saying that bareshafting is "The End All Tuning Process". I'm just saying that for hunting purposes and getting fixed blade broadheads to fly great , the bareshaft process has worked
B..E..A..UTIFUL for me.