Do the charging cables really fall outside any testing requirements?

As I recall, the Electricity at work regs don't specifically demand testing at all - but simply demand duty holders ensure that all systems are kept in a safe condition - periodic testing is just one (if very common) way of demonstrating that the requirement has been achieved. So the statement is possibly technically correct, even if likely to be misleading without a fuller context.

   - Andy.

Is it because vehicles come under Construction & Use regulations?

I can believe a 15% loss from mains going in, to DC power coming out of the battery.  The process isn't going to be 100% efficient.

This appears to apply to the low power AC charging cables with a connector at both ends. For a private user it will probably just be abused  until it fails, for a business user there probably should be some form of risk assessment. How great is the risk if a live conductor becomes exposed? As I understand it all the likely sockets the cable could be plugged into will have RCD protection. What will happed if a live conductor starts to break giving a high resistance 'hot spot'?

The higher power charging cable that are fixed to the charger hopefully have some sort of testing routine. 1000V 500A capable systems are in use and 1MW systems are in development, but these should have suficient internal monitoring to minimise the risks.

As already mentioned if its a private vehicle, then owner will likley just let things go till protective devices trip and they cant get car charged or there is a pop as the lead fails.

If its a company vehicle, then the vehicle and its lead are part of the company assets and as per HASAWA and general work supplied equipment needs to be "Maintained" by the duty holder. Now that to me can be a simple induction, memo, info seet to users of the EV's that before using any charging lead it appears to be in good working condition, no frayed/damaged bits, just exact same as the "User" checks that are meant to happen when employees use electrical equipment. There then should be some form of "Formal" inspection and test, and carried out by a competent person and results recorded.

For high powered chargers where the charging cables are tethered, then thats down to the owner/duty holder of the charging equipment to make sure those cables are maintained.

I think what Im saying is to do nothing and not inspect those elads formally or have written procedures for maintaining them, then the fleet operator could get into a bad place if the user has an electric shock or worse.

Cheers GTB