I think in terms of tackling technic there will be many more occasions where the hips are above the head.
If a players legs are on the ground you can't physically spear or tip tackle them.
Lifting the legs is where the issue comes I. As it maybe fine bit it can easily go wrong as other players in the tackle and the tackled player themselves cant then control the tackle with forces moving in many different directions.
I think the refs have a duty here as if motion is stopped, the call for held should be quicker.
There are many times were the motion is stopped and whilst the players continue to wrestle no held is called, resulting in very late offloading or tacklers continuing to wrestle or lift in an attempt to complete the tackle.
For me if forward motion is stopped then that should be held.