I think this whole deal of objectivity is taken out of context and frankly, irrelevant. I also don't understand all the arguing over which system is best. Determining the best system is very easy. It's whatever system the individual player thinks works best for them. It's no more objective than who makes the best cue, who makes the best chalk, etc..
The edge of the OB is clearly objective. Frankly, the center of the CB is only somewhat objective IMHO. The A, B and C aim points are most certainly not objective if you want to be technically pure about it. Then you get the 1/4 and 1/8 ball thin cuts with CTE/Pro One that cannot be argued as objective. They're no more objective than if you were aiming at those using fractional SAM. But really, why argue that point? The vast majority of shots taken during the course of playing involve CTE as a primary visual. Having used other aiming systems, I believe that is at least the most objective visual you will find in any aiming system.
IMHO, the biggest challenge with CTE/Pro One is learning the pivot. With Pro One, this ends up involving some precise moves. I believe that is what is consuming the time with most people. Stan shows bending over as one of his pivots. But what does that really mean? I can say for sure by trying it myself, it isn't simply a matter of bending over. Rather, it is a matter of bending over whatever amount is necessary for you, the individual player, that takes you to correct CB position. That, I believe, is what takes the most table time.
CTE/Pro One is no more of a Silver Bullet than any other aiming system. It has some exceptional strong points and advantages but it requires extensive table time, like any other system, to become proficient.