Yeah the tv adaptation really screwed up the dynamic of that scene and arya as a character at that point of her development. if they know that they aren't headed to gravedigger vs sir robert strong for cersei's trial by combat then they should of just had arya finish the hound off. I mean i guess its good that they left themselves an option, but if we're losing the ironborn, losing aegon/connington, losing 90% of the dynamic in mereen i just don't see cleganebowl surviving the cut.
It's a case of loved the tv adaptation but they lacked the conviction to see it through. the adventures of arya and hound, especially the hound, just killed it all season. but if you are going to extend their time together, have them bond, become her protector, and take those wounds defending her from what they saw as agents of the lannisters they should of had the balls to say "you know what, we're not going to marry this back up to the book scene. It just doesn't make sense now with what we've done with it."
The hound could of rolled off into that gorge and got swept away by a river, pod could spent the entire scene chasing arya down to the point that she gets too separated to go back and check on the hound with pod after her and brienne closing ground, could of handled it a dozen other ways that left it open ended to the hound's fate without making arya a cold blooded cunt about it.