I suspect what they meant is that there isn't an official Schuko nub that slides onto the brick and lets you hang it directly from the socket rather than carrying an extra meter of cable around. There is a BS1363 one, and those are only legit feasible in a grounded configuration (although I guess you could use a plastic ground spade to lift the child protection slider inside the socket if you were a particularly unpleasant engineer). Nice for those of us in British-adjacent countries.