There was no "standing" in the endzone. And the USU player was not pulled down. There was handfighting. The USU player made no attempt to jump. Watch his legs. He was not held down. He was a third grader getting owned by a much bigger body. You are not going to get PI there ever.
By the way...what were your thoughts on the no taunting call when 17 squatted over Kurtz and made the incomplete gesture several times?