It is more than convention, the /64 is the minimum allocation to support SLAAC. If you're getting less than a /64 you're not getting full support for IPv6.
Well you're not getting support for SLAAC but I didn't understand that to be a core requirement to qualify as a functional IPv6 implementation.
Regardless, my point is that allocations narrower than /64 exist in the wild for better or worse. So do IPv6 NAT implementations for that matter. If you assume either of those things don't exist then you might be in for a surprise.
Well you're not getting support for SLAAC but I didn't understand that to be a core requirement to qualify as a functional IPv6 implementation.
Regardless, my point is that allocations narrower than /64 exist in the wild for better or worse. So do IPv6 NAT implementations for that matter. If you assume either of those things don't exist then you might be in for a surprise.