It does, but not all have one, or it is in a very non-obvious place, so non obvoius you could miss siing it at all during installation.
In any case, that was not my original point - what i was saying, was that with modern loading it is possible to overheat the cable at one end of the ring and not the other, but in practice there are not enough real incidents to warrent a change of policy.
In the same way, non fused spur with a double socket could be overheated, and nothing would blow, but there are not enough accidents to warrent a policy change there either.