I disagree that he is not impeding the defender; you can clearly see him pulling the jersey for over 50 YARDS, that is absolutely going to slow him down. The restriction is going directly away from this camera angle (IMO) as he is being forcibly restrained from reaching the runner.
9-3-3b. Holding. The hand(s) and arm(s) shall not be used to grasp, pull, hook, clamp or encircle in any way that illegally impedes or illegally obstructs an opponent.
I'd say that grasping and grabbing are the same act, and I'm sure you would agree, leaving the last part of that rule to be relevant. Was he illegally impeded or obstructed? I would say yes.
For holds, what I have been told is that from its location on the field, it has to have a material effect on the play, and the player must make an effort to get away from the restriction. Is that a philosophy thing, or is that a generally accepted interpretation of illegally impeding/obstructing, or located somewhere else?
Just looking for more context on why it is, the way it is.