[greymule]

it is not a catch if the ball has already crossed the boundary

Where is this in the NCAA book?

And I'm having a hard time understanding the following exchange:

If the body is partially over LBT, but the catching hand is over DBT, and the body lands in DBT, is that not a catch?

Correct.

In a lifetime of playing ball, I have never heard anyone contend that a player who jumps into the air from fair territory, catches the ball partly or even completely over DBT, falls into DBT, and holds onto the ball has not made a legal catch.

If breaking some sort of "plane of the fence" applied, then a player couldn't reach over the fence to catch a ball in the air--something that is done all the time.