This is just talking about games approved through Valve's verification process. There are a lot of games that work that are "unverified", not to mention the entire history of gaming available through emulation.
The worst thing that Valve has done is "the main kernel tree hasn't gotten around to merging some of the Deck's EC bits yet". You could run Batocera or Bazzite on your deck today if you want. You probably don't want to, those distros aren't as good an experience as SteamOS yet.