I have no idea where that list is coming from but many top games are missing. Fortnite, League of Legends, Valorant, Roblox, FC26, and Battlefield 6 all do not run at all on Linux due to anti-cheat.

It's based on Steams numbers, so yeah games like Fortnite, LoL, Valorant and Roblox won't show up at all since they aren't distributed through Steam. Battlefield 6 should be on there though, maybe ProtonDB just hasn't refreshed the stats in the few weeks since that came out.