That's only the student section.
And it's really no different than any other game I've ever been to. Students at UT stand for the whole game. I mean, they don't do it for pride or tradition so they'll sit down during time outs or when they need to pour more bourbon from their boot flask into their stadium coke, but while on-field action is occurring, I can't recall a single stadium I've ever been to, where the students didn't stand. They stand at Tech, Baylor, TCU, Houston, Arkansas, and of course at the Cotton Bowl for TX-OU. Heck, what few students I ever saw at a Rice game, were standing too.