A move operation is representationally an atomic copy and delete.
The original object is clearly no longer there.
It's clear cut breaking backwards compat for no reason at all.
I don't even know why they aren't supporting both API versions indefinitely it doesn't really make any sense it's literally a url rewrite/301 for anything hitting the old domain. Want to avoid our bottleknecked legacy LBs for better performance? Hit the new LBs. Hell even the sdk doing this upfront will alleviate a crap tonne of legacy requests.
People need to stop allowing corps making breaking backwards compat so nonchalantly it's unprofessional. And on top of that, AWS has a really good track record of maintaining backwards compat, allowing them to get away with this is just asking for more down the line.