The [connection].interface-name setting can't be handled IWD (e.g. during autoactivations performed by IWD) and although for manual activations NM will probably check it, there's no reason for the IWD backend to restrict new profiles to one interface plus when running IWD the udev permanent interface naming is likely to be broken.
I wouldn't mind if this got merged into the new nm-1-32 branch too.
See also #743 (closed)