

There were some games that can be run on Steam Deck, but will not run on other Linux systems, I think they might be able to do similar stuff for the Machine.
IMO I think it is just limited the game’s visibility, but ultimately it’s up to the game devs. (Like tech support or “fairness” reasons)
EDIT: This list show games that only run on Steam Deck or SteamOS, but not other Linux systems https://www.gamingonlinux.com/anticheat/status/steamos/
It were possible but it’s more on the developer side at that moment.

Yeah, one of the game I thought is Infinity Nikki, another one is Delta Force.
I updated my comment to include a link to the list about which games have restricted Linux system(s) support.