I didn't even know HDMI extenders over IP existed! I wouldn't use it for TV/movies, because the re-compressed picture can't look all that great. But I could imagine plenty of uses for something like that!
HDMI is in fact the RAW color values, uncompressed. Each of the color channels are serial, but that doesn't really change anything about the raw bitrate.
HDMI video signal is uncompressed but not raw.
I agree that the bandwidth overhead of 8b10b can be dismissed in context, but nevertheless disagree that the underlying functional equivalent of HDMI blanking can be entirely ignored given that's where the audio stream is embedded, with a max +/- 2 ms delay relative to video requirement.
To your point, it's unclear in my mind that even a hypothetical 3 Gbps Ethernet PHY would be sufficient in practice to transmit raw 1080p60 + stereo audio without some form of compression given framing and IP stack overhead, which certainly isn't free; i.e. you'd be at 92.7% link saturation in a completely lossless environment just blindly transmitting raw 1080p60 video data without framing or audio or IP encapsulation.