Ooh- that's a 'clever' one You are technically correct - in which case you'd better be telling that those in this forum and elsewhere who often advise an 'indoors' DP switch for outside sockets supplied from ring finals! As for how sensible it is to distinguish between a DP switch and an FCU is this way is something I will leave you to ponder!Don't know if you are allowed to use a DP switch on a RFC, I think they are built to a different British Standard number as to those allowed by reg 433.1.103 or any given in appx 15
Kind Regards, John