You can send a cease and desist for any reason to anyone at anytime.

But they wouldn’t be able to win in court, the eula of both games explicitly allow using their IP in mods

In short, they’re trying to make much more money to pay the executives’ 7 figure salaries, and are giving up browser privacy to do so.

You’re almost definitely thinking of xiaomi, which almost always sell as unlockable carrier independent models.