Because some people are claiming that they all work, and Valve is saying that they plan to have every game working with Proton by the time Steam Deck releases. I've lost count of the amount of times I've seen people point to the "15.5k games work" number on protondb since the Steam Deck was announced, even though "15.5k games work" only requires a single person to say a game worked for them, and less than half of games on the site are rated as platinum.

>Because some people are claiming that they all work

Who? Just go to that site. It's tells what's working and not working. It says right there on the front page only 50% of the games are currently rated gold. You can't really complain that something doesn't work when they're telling you it doesn't work.