My boss told me to use PVA glue for a full leather binding and it was a disaster.
He said it would be fine for a quick job, but after a year the spine cracked and the boards warped. Should I have pushed back harder, or is there a time when PVA is actually okay for leather?
Yeah, you should have pushed back. PVA dries too rigid and doesn't move with leather over time. It's only okay for cheap, temporary fixes you don't care about lasting.
I used to grab the PVA glue for everything, but @derekjackson is totally right about it cracking. I ruined a good belt that way last year, so I don't touch it for leather anymore.