I feel as nfl refs have not ever played the game , they just know the description of the rule.
If you have never played tackle football in pads, you could never understand what you can and can not to do once u commit to hit someone. Players are used to playing a certain way for 20 years , hard to break those habits. Seems like these refs jut dont understand that some aspects of this rule are unrealistic at full speed.
Replay would only make this worse , it would be like the catch rule last year. Once you watch a catch is slow mo , it's too easy to find flaws or see the ball moving.
I dont like where this is going , I hope these pre season calls are just to make a point. If not this can cost teams wins.