It’s not the gotcha that they think it is. Increasing share of Linux, steam deck or not is progress. Any development or considerations made for the SteamDeck and its Arch based OS benefit the non SteamDeck Linux gaming scene too.
Mostly a stab at Reddit PCMR, Lemmy PCMR has a different vibe.
People count Chromebooks as ChromeOS even though it is Linux.
ChromeOS is not counted as Linux for the same reasons Android isn’t counted as Linux and MacOS isn’t counted as BSD. Those are proprietary, locked-down operating systems. It contrasts with what is broadly understund as Linux, meaning Linux distributions that adhere to some kind of FOSS philosophy.