I see now that you are referring to a post relating to a penalty kick at goal....I thought you were referring to a conversion as per the original scenario. Apologies and thanks for clarifying.
So it's OK to latch on to the ball carrier and 'accelerate' them into contact but not push them!
Edit.... Obviously the referee is the final arbiter of fact and if they decide it's dangerous etc then so be it!
Maybe Ref was stating that the AR had chosen to change the mark or maybe Ref was overruling the AR which he is entitled to do.
I think the only scenario where the throwing in side can move back inside the 22 is in the case of a quick throw in and then they are deemed to have taken the ball back...