The fact is, it really sucks and they should have limited it to maybe a subset of two... one that can only deliver basic charging and data, and one that can deliver all features. A $5 sku and a $25 sku (or close to). Unfortunately, it's all a mess.
> (at least in manuals)
... and come to think of it, why not colored rings around each end of the cord? There aren't that many features.
"2018 MacBook Pros support green-purple for the highest feature set"
Far simpler than things people use every day: https://en.m.wikipedia.org/wiki/Electronic_color_code
There are only six variants: https://people.kernel.org/bleung/how-many-kinds-of-usb-c-to-...
And it's actually the product of three variants (2.0 only, 5 Gb/s, 10 Gb/s) by two maximum current ratings (3A, 5A), so a pair of logos would be enough.
I get not physically keying: that's the whole point of the USB-C idea.
What I don't get is why the hell they didn't mandate standardized identification (at least in manuals) regarding port / cable feature compatibility. The entire point of the trademark is to use it to make things easier for the customer and promote adoption.
Make a logo for every feature (4k 60hz!), trademark them too, then mandate implementers advertise featuresets via the logos. Problem solved.