It scared me more when Texas's offense and defense would move around a lot pre-snap. How is that even legal.
The difference is a shift compared to motion. As long as the QB hasn't started the snap count, as long as the players are in a legal formation to start (7 men on the LOS) and are set for a count, and as long as after the players move they reset for a count you can shift all 11 players if you want to. Then you can start your snap count and send a man in motion, which UT often did.
Granted, UT's offense (particularly QB) struggled a lot, but their switching of formations, shifting, and motions put a ton of pressure on a defense. Its really an amazing switch from their previous OC who really didn't do any of that with their scheme.