I have a few modular power supplies around from different vendors, and I made the mistake of using one cable in a different vendors supply.
The supply side had the same connections; so I thought that I could just mix-and-match.
Turns out, that even though the connections are standardized, I ended up putting ground on a 5v pin, 12v on the 5v, 3.3v on the 3.3v (magically) and 5v on the 12v pin on a standard SATA connector.
As a result, I fried several hard drives, because the output of the supplies wasn't standardized for the connector type. I can't even imagine an end-user using a volt-meter to check which are compatible with which vendor.
This was a problem before USB-C.
TL;DL: Check your modular supply cables, and don't use other vendors cables.
USB-C on the other hand is a standard.
It used to be the case that anything of the same connection type would - at worst - not work if it wasn't designed for that piece of equipment. But now you have a situation where things "kinda" work together so consumers are encouraged to mix and match yet some of the time it could literally break your hardware.
So now we have a situation where some people are too scared to mix and match which breaks the entire point of a standard connection type - and on the flip-side you have other people who are left with bricked hardware because they were unlucky enough to plug the wrong charger with the wrong device (for example).