I think it's the bats coupled with hanging breaking balls. I was pondering the difference between an MLB pitcher and an above average college pitcher, it could well be a combination of control and being able to change speeds effectively when needed. The breaking stuff in college usually LOOKS pretty sharp, to me on TV, but at times they leave them UP in the zone, and they leave the zone with alacrity.
The velo seems about comparable.
We see even elite MLB pitchers at times have a bad game, it often seems, to me, to be 3-4 pitches misplaced by a few inches.
We use wooden bats in my league. The fences are pretty short, like 300 down the line. I've seen one HR so far, a slam. It was a shot, I was playing 1B at the time.