Rob, I'm probably the one that started all this - I mentioned my son was throwing guys out at a clip of 70 plus percent and in truth he has been. He is at the JV level and most of the pitchers are fastball pitchers and my son calls the whole game including a move to 1st. I think those two factors help keep the runners close.
Also, it seems many of the opposing coaches try to steal a lot and actually hurt the runners chances based on that. At the varsity level, it seems coaches are more deliberate on the steal which to me would drive their stolen base average up. So as Fungo says, so many things go into the SB average with much of it outside the catcher’s control.
I do like the idea though of perfect throw, in time, dropped by infielder as an error to the infielder - when I own the world I will make that change
PS: Last night our pitcher was a junk ball pitcher and my son was 0 for 4 in put outs – oh well.