Here's the GIF showing the play in the BYU-UU game and the clip that the NFL uses on their web site to show a textbook example of defensive holding
(NFL rules at https://operations.nfl.com/the-rules/nfl-video-rulebook/defensive-holding/):
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Also of note: NCAA football rulebook Part II, Section 8.8 and 8.9 lays out the conditions for Defensive holding (emphasis added):

8. A grab of the receiver’s jersey that materially restricts the receiver and takes away their feet should be defensive holding if other criteria are met, and could also be defensive pass interference.
9. Holding can be called even if the quarterback is subsequently sacked, and there is an element of time between the foul and the tackle.