Don't forget that there's another ruled called the spearing rule.
Article 8(f) states in pertinent part:
"If a player uses any part of his helmet (including the top/crown and forehead/”hairline” parts) or facemask to butt, spear, or ram an opponent violently or unnecessarily. Although such violent or unnecessary use of the helmet and facemask is impermissible against any opponent, game officials will give special attention in administering this rule to protecting those players who are in virtually defenseless postures . . ." (Emphasis added.)
Accordingly, it is unnecessary roughness to "spear" (i.e., use the helmet as a weapon against any player) on any play, regardless of whether the player is in a defenseless position.
Under that rule, if the ref deemed that Harris was going up with the facemask part of his helmet at the chin strap of the opponent, they can still call a penalty (just under a different rule.)