The freeze frame of the moment of drop had the runner's extended left right just at/above the goal line, so the ball was easily well short. Now whether it was 1 yd or 3/4 of a yd? Who cares. Cal's ball on the 1 yd line or the .75 yd line or even the 0.5 line, but no chance it was over the goal line. Game over...score more pts next time, TX.
Edited to add: photographic proof....ball is already well out of his hand and still closer to the 1 yd line than the goal line. And neither of the two TX dudes even attempted to pick it up, the 3rd guy on the scene did - and that was only to give it to the ref. That's not in the immediate continuing action to me.
https://pbs.twimg.com/media/CsncxhmUAAAI0pX.jpg