Valve initially greenlit this mod back in 2017, and then went radio silent and just stopped communicating with the devs for 5 years before pulling this C&D.
The bootlicker mental gymnastics blaming the devs for valve not communicating or updating the SDK is infuriating when the TF2 mods that were barred on these grounds are currently in the process of being released on steam.
It's more than likely just gross incompetence from valves flat structure management.
Also Valve doesn't need to do anything when they have such a pervasive cult of personality.