This affects 100% of linux boxes with an hdmi port, so valve is making a tiny fraction of the impacted hardware.

My point was that the HDMI Foundation/Org isn’t going after hobbyists at home.

But if a hobbyist were to sell an unlicensed HDMI 2.1 box then the IP holder would likely go after them.

In their eyes, in that case, the IP is being pirated.

This is very similar to h.264 however however in that case the standard is public, commercial use requires paying a fee. Licensing of the HDMI 2.1 specification requires an NDA for specification testing that Valve is not able to perform in order to say that it is a HDMI 2.1 compliant system. They would be running afoul of the HDMI org’s licensing terms.