They're called 13A sockets because that is the maximum current they can supply.and that adds up to even more of a reason not to call Bs1363 sockets ' 13 amp sockets' as regardless of the supply avilable it;s the only 'standard' UK socket to most people.
Having a power socket rated for a higher current than can be delivered is normal. You should never assume that any socket can deliver the full rated supply. It's no different really to how most household mains cables will be rated to carry 450V.