Ever heard of TCP/IP over HDMI? It’s a method of exploiting HEC. Connect your smart TV to a streaming platform and it connects to the internet via the video cable. There’s no escape.
Overall it’s not a bad idea if devices need network connectivity. Have one central “box” get an Ethernet drop and it acts as a switch for your tv/xbox/playstation/media player/etc. The spec was made back when A/V receivers were more popular than they are now. It would cut down on a cable per device.
If OP means an exploit/hack then that’s a bit different.
AFAIK it got not used, or not implented in relevant ways.
So far...