Similarly to hip drop tackles, horse collars are unnatural to the game and are decisions players make when in action. There is a reason why the horse collar rule has basically eliminated it from play (like less than one per team got called last year).
When you talking about grounding or PI, those are natural penalties. Those are going to occur, and there will be varying degrees of such.
You won’t see very many hip drop tackles moving forward, because players will no longer decide when in action to hip drop someone, just like they do on literally more than 99% of the tackles they make. It’s a very deliberate act, and as Rouxable compared it to, is similar to flat out deciding to drop kick your opponent.
That Kevin Dyson/Mike Jones play is nowhere close to a hip drop.
I think maybe the term “hip drop” is what’s confusing people. Maybe it’s not descriptive enough.