I said PHYSIOLOGICAL, not PSYCHOLOGICAL!!
But seriously, it doesn't seem there would be much of a difference between a bar resting on a board, which is laying on your chest, as opposed to the bar resting on a set of pins. I understand training is a science but you can also look to deep into training techniques as well.
im not a fat powerlifter but here's my guess:
-even slight differences in exercises allow you to rotate through exercises in 2-3 week rotations to avoid overtraining
-benching with a board feels more like a real bench because you are resting the weight on the body
-It doesn't require setting up in a cage which can be time consuming
-It allows better control of the range of motion, whereas pins in a power rack are fixed in place
-It's another way you can piss of Coach by doubting its effectiveness