Yeah, Display Port is old, but I've never seen that P and D symbol before, or at least never noticed it. And, even if it existed before Display Port over USB, you'd think that that potential confusion was a good opportunity to come up with a new logo for something that would be put next to a USB port.

It’s almost as if having all these different features would be easier to differentiate if they had different physical shapes.

I think the goal was always that you'd only ever need one type of port and one type of cable and that that port and cable could do anything. Unfortunately, because there are so many revisions and so many features are optional, you've now got a situation where the port is the right shape, the cable fits into the port, but you can't get the thing to work without reading the fine print, or without decoding obscure logos.