To be fair, that was likely some first level support reacting to you trying something that is not supposed to work, as in not supported (playing on Linux).
How the strategy pans out after those talks we will see.
This just in: Rockstar Games announces GTA 6 and RDR 3 will only be available on Rockstar Social Club.
Valve isn't powerful enough to force big publishers to stop their anti-consumer practices. They will just use their own store, and Valve will lose a revenue stream.
That may very well be the official stance, only officially supporting SteamOS in much the same way games used to only officially support a single major distro, often Ubuntu. However, I don't see it actually stopping you from playing on other Linux systems. The functionality is there at that point. It's just a matter of making sure you have whatever it depends on from the Deck.
See this going around and... that is a LOT of reaching from a random CSR trying to placate an angry user.
"We are currently working with Rockstar games to find a fix" followed by "You can buy the game you already have for cheap" just means that Valve sent an email saying "Bro, what the fuck?". And Rockstar will likely send a response of "Do you want GTA 6 or not?" and this will never come up again.
I would like to be proven wrong (GTA:O is trash but some people like it) but ... not optimistic. And we get these kind of "A random CSR said something to make me stop asking to speak to their manager!" level of "leaks" a few times a year. The vast majority go nowhere.
Oh HELL yeah. That means if we get some way to run Battleye on the Deck I can finally get Siege working both on the Deck and on my Linux partition and Windows can gtfo