Indeed. The bigger problem is also that consistently the most played games are multiplayer competitive titles with anti-cheat software that is only written for Windows (and sometimes MacOS). I suppose this issue will solve itself, once enough people start playing on Linux. Then developers will be forced to support that too in order to not lose too much of their player base, but we are still a far cry from this threshold.

That would mean that it still would be around 0,5%. If you want to split the hair probably 4,5% of this 5% is Steam Deck.