USB is just a complete mess. I don't mind so much ports having different capabilities if they are well documented in the specification sheets of the hardware because then at least I can find out what they are capable of, but alas it never seems to be the case. Its very hard to work out whether a port can do Displayport and to what extent/performance or its true power capability or just its real data transfer speed. More often than I like I have just hoped that something works. Anything above 5W charging and 5gbps transfer is optional.