Well the rule states the following:
Section 4 - Legal and Illegal Contact with Eligible Receivers
Article 3. Illegal Contact Beyond Five-Yard Zone
Beyond the five-yard zone, if the player who receives the snap remains in the pocket with the ball, a defender cannot
initiate contact with a receiver who is attempting to evade him. A defender may use his hands or arms only to defend or protect himself against impending contact caused by a receiver.
Emphasis on the part in bold / underlined - initiate contact. Now, I have watched the videos, and the quality of the better angle / above is not good. So, this is just what I am seeing. But, it looks like the defender initiates contact with his left hand and Trent flicks it away with his arm (I do not see Trent's arm motion / flick, but the defender kinda waves his left hand up and out as you see above, and I think that is in response to Trent kind of flicking it away). Thus, and again, based on the poor quality of the video above (no offense to the camera operator) if you are going to make a call, by rule, it ought to have been illegal contact because it looks like Trent is running and the defender initiates contact.
Further, it does not look like one can make a strong argument that Trent initiates contact and or that the defender is protecting himself against impending contact based on the angles each player is running (can compare using the numbers / sideline / and starting-ending positions between the 45 and the 40). Trent seems to be taking a shallow angle toward the sideline (view his approximate distance from the Rams' sideline between the 45 and the 40) and compare it to the much sharper angle the defender is taking. The defender's angle "cuts off" Trent's route, and to me, it is the defender who is initiating contact.
Section 5 - Pass Interference
Article 1. Definition It is pass interference by either team when any act by a player more than one yard beyond the line of scrimmage
significantly hinders an eligible player's opportunity to catch the ball. Pass interference can only occur when a forward pass is thrown from behind the line of scrimmage, regardless of whether the pass is legal or illegal, or whether it crosses the line.
Based on the definition, I do not see how it was PI on either guy.
[ Edited by Polkadots on Sep 23, 2017 at 12:53 AM ]