I agree 100%. Next to absolute arrow integrity, arrow flight is the next most important factor in tissue penetration (at any given impact force).
All the arrow design features that maximize penetration are useless if the arrow suffers a structural failure OR if the arrow flies poorly. These two things MUST be in place before you gain anything significant from the other arrow design features.
Arrow integrity comes in first because any damage, any failure, in the arrow system severely limits penetration AND terminal lethality; such as a shaft, insert, broadhead adaptor or broadhead that bends or breaks on hard tissue impact. The other arrow features that enhance arrow penetration, perfect flight included, can only come into play if the arrow remains undamaged at impact and during penetration.
Ed