The standards the UK adopted pass higher voltages and higher currents per household circuit than pretty much anywhere else. They adopted standards that allow them to use use less wiring, less copper to provide the same energy. They can plug in many space heaters on one circuit, where two or three would blow a breaker on a US circuit.

That higher voltage and higher current makes their household circuits inherently more dangerous than household circuits outside the UK. A fault in a UK circuit passes a lot more energy than a similar fault elsewhere, before tripping a current-limiting device. The exact same fault in a UK circuit is far more dangerous than in a circuit pretty much anywhere else in the world. The standards for household wiring in the rest of the world are a lot more restrictive than the standards adopted in the UK.

UK plugs on Japanese appliance in Japanese houses (for example) are overkill. The safety provided by the UK plugs is built into the Japanese breaker panel and wiring. Putting the UK plug/socket into a Japanese circuit provides no significant additional safety benefit. The Japanese plug/socket on a UK circuit would be extraordinarily dangerous.