I believe we too often do not rule OPI because an offensive player did not CREATE separation. I have seen many cases (i have probably done the same) where we let the offensive player MAINTAIN separation thereby preventing the defensive player from making a play. There was definitely a slight push in the video. Does the push rise to the level of creating or maintaining the slight separation required to catch the ball? I am not saying it does or doesnt in this play. I am simply saying I dont believe one has to CREATE separation in order for there to be OPI.
If I take a pass on these plays, I always tell the receiver, don't make me judge whether or not you pushed off. Play the ball and keep your hands off the defender.