Well I guess you're right in the sense that everyone is different and the mechanics of the lift will changed depending on arm length, shoulder width, thickness of chest, blah blah... So therefore some people are better benchers than others genetically. However, this BS gets way too complicated. If you touch your chest you will get the best effect as far strength gains and chest size/arm size... I would say.
This is not to say that you can't mix it up and do some board presses, dips, tri extensions, DB chest flyes, floor presses etc etc. They all have their place.