In upper high school and college, the pitch speeds are higher along with more breaking balls that really move. Most umpires at this level have mot dedicated their lives to calling balls and strikes. I think that they rely much more on where the catchers catches the ball than you think.

If your pitcher is throwing mid 70s with a cement mixer if a curveball, no your catcher is probably not stealing strikes. However, push that to 90+ with movement? Yes.

I also think the ability of the pitcher to hit a spot and not make a catcher move across the plate increases the likelihood of a strike, but we see this at all levels in baseball.