I think we are diverting from the original question here and trying to justify not doing something because its unheard of.
Are recessed UK power sockets not compliant with BS1363? Is there a rule saying that they cannot be recessed into the wall?
I'd imagine they could be manufactured to meet BS 1363, but there wouldn't be enough demand.
They work in the U.S because of timber framed houses, there aren't enough framed houses here to justify producing them.
You'd be into the cavity trying to cut a suitable hole to fit them and more likely clashing with building regs than B.S. compliance.