That's not the case where I hunt. Heck a 7yr old buck might still only be a 130. We don't have the genes or ground to grow them like the midwest. Though I was reading an article not too long ago discussing the many different subspecies of whitetails in the US. That could have more to do with it than people realize.
That's a big part of it
TN. Our Southern deer don't need a big body mass to survive the winter. So they haven't evolved in that direction.