That's how data cables/ports work. There is a DisplayPort "protocol", then there are DisplayPort physical connectors and cables. Then there are other types of physical connectors and cables that also can be used with DisplayPort "protocol". Same thing for USB, or HDMI etc.

Yes, it's confusing. But it's also a good thing as you can carry lots of stuff over the same cable and connector. A USB-C type cable and connector can carry USB, Thunderbolt, DisplayPort, HDMI, even analogue audio.

Before USB-C, Thunderbolt was using mini-DisplaPort connector and cables.