You can see he throws it mid-play, intentionally, when contact was made. So he clearly thought it was PI. Curious why you think they picked it up?I don't think refs do that is what I'm saying, if that was standard protocol then wouldn't we see them pick up flags for PI, or offensive holding, etc. if the foul ended up not mattering more often? When an OL holds but the QB still gets sacked they still call the penalty and have it be declined.
Most of the time when they pick up flags it’s because the ref who threw it was overruled or it fell out of his pocket on accident. There was no other ref in the vicinity to overrule this.