Title says it all, really. It'd be a nice touch to stop the tree growth animation in the hopping bonsai pot when the inventory below it is full and then starting it when there's space again.

I do not understand. That's exactly how it currently behaves.
Progress of tree growth is only reset to 0 if the Hopping Bonsai Pot was able to insert one of the drops into the inventory below.

How did you test this?

I've tested this with crates from immersive engineering and storage drawers. I'll do some more testing and get back to you