Didn't see any fans around me at the match admitting as much. Can you provide some examples of when Mayo were doing it? From Kerry, it was literally every time a Mayo player broke a tackle between the 45 and 65 in Kerry's half.
Separately, the way the rules are drafted for the black card, the player has to be 'dragged down' in order for it to apply, which implies that the player has to be brought to the ground rather than merely 'dragged back'. In my opinion the spirit of the rule should be that being pulled back merits the black card, or else it's not worth using at all. Also, there's no difference between a rugby tackle to bring a man down in front of goal and the tackle on Vaughan for the penalty. Either use the black card for both or not at all, the intention to bring him down is the exact same regardless of method.