Sounds like the players don’t like the rule because it’s confusing, which is my main complaint about it. The NFL stated that they believe it will result in fines more than flags because it’s difficult to identify at game speed. Which again means the rule is vague and confusing. There’s 3 parts to it with third being the key part I believe, Landing on the ball carriers lower legs below the knees.
The NFL watched the past two seasons and identified 105 hip drop tackles among 20,000 tackles in 1,088 games. That’s one hip drop every 10.4 games and one out of every 190.5 tackles. It’s not a common occurrence or a go to tackle for defenders. If it reduces serious leg injuries, cool. Just make it less confusing and better explain it before implementing it.