Peer-to-Peer Blocking with interface groups / AP groups
I think when this feature (P2P blocking) was added, there were no concept of interface groups, etc to map multiple vlan to same SSID. When additional features added the original P2P blocking was not optimized to work in all these scenario.
This is a one feature I am not trusting well. I think it has drawbacks like what you found. Haven't tested in detail, but heard lots of issues with this feature.
Open a TAC & confirm with them what is the expected behaviour in your situation