They've already done that afaik, like warning about charging at slower speed.

Some chargers will re-negotiate depending how many cables are plugged into the adapter. Which is fine, but sometimes makes it tricky to know if it's the cable, the plug, or the number of cables causing a slow charge

Haven’t ever seen a warning like that in KDE.

The hell Apple or Google cares.

Apple should care because customers will blame slow charging times and slow transfer speeds on the phone

I think Apple much rather tells users that this is exactly what they warned them about when they were forced to support USB-C and will advise users to only buy official cables from Apple.

You mean USB-C, the standard that they largely led development of?

No, they mean USB-C, the port they switched all but a handful of their devices to before any other manufacturer.

While GP’s take is ridiculous (if common), I do think the notion that Apple led the charge on USB-C is mostly a myth, outside of them being active participants on the USB Implementor’s Forum.

Eh, I can’t find it now so a thousand grains of salt, but I read a good article back in the day about how much Apple’s experience with in-market Lightning shaped USB-C’s physical connector and electrical handshake.