You are right. It is good to use the short version when the cross-up fails, so it is safe on block. I’ve seen a bunch of YuuVega footage yesterday, and he uses it that way. When it connects, he uses psycho crusher. I suspect this is due to the high stun on the aerial attack: the knee press will dizzy on the first hit, so psycho crusher ends up doing more damage.
I know Chun, Claw and Dee Jay are thin, so the full cross-up combo does not work on them. I ain’t sure which ones work on who, though, and it is not in the wiki, yet.