This is at least partially related to HDR10 is there or was a gimmick?
The USB-C video port implements HDMI alt-mode (and nothing else if I have understood it correctly).
The USB-C power port implements a standard Power Delivery sink (with a pretty uptight policy it seems as people have difficulties having power contracts negotiated from fairly common chargers like Apple ones).
Edit: The only video alt-mode supported by the PPM USB-C video port is alt-mode DP, not HDMI -> Connecting laptop using USB-C cable