There are even bigger caveats to that number than what they mentioned in the video. Since all the ratings are based on user reports, there is no standard for what is considered a working game. You can look through pretty much any game and find positive reports that mention frequent crashes, performance issues, missing textures, requires a custom proton version, etc., but since it launches, they gave it a thumbs up. I've tried platinum rated games that are completely unplayable, ProtonDB ratings are a general guide at best.

ProtonDB also considers a game as "working" if even a single person gave it a thumbs up, so the big "17,984 games work" on the home page is very misleading.