it's quite simple, for weapon-x (lets use that as an example) you CAN'T have any lag.. or logan will miss his targer on one screen, and connect on the other...
while moves like skinkuu-haduken, or ANY of the hyper's by Chun-Li don't require that... they look/act/perform in the same way no matter what you see on either screen...
this is the main reason why we STILL dont hae throws in the game