Sounds like he's approaching the inflection point of personal risk/ reward. $55 mil for another season? Crazy money but he should already have generational wealth and he's probably realized that winning in Cincinnati ain't gonna happen.
I can't opine on the translation of musculature to arm strength but yeah, it probably doesn't matter much.
But if you want to survive in the NFL at a position that regularly takes hits, 180 soaking wet probably isn't an optimal strategy.