Is it too little, too late? Microsoft now owns a lot of the biggest game franchises through the Activision and Bethesda acquisitions, and I wouldn't be surprised if they actively block Proton support by using UWP or Windows-specific anticheat.
Surely this wouldn't make any sense for them strategically? They want as many people playing and making noise about the franchises they own as possible - especially multiplayer.
If Microsoft locks down their environment, I believe they are in danger of losing their dominance on PC.
I have yet to meet a developer that likes UWP and I believe it is dead by now. There is WinUI 3, but I fail to see how they learned from their mistakes. They believe they can work it out with rebranding, but I heavily doubt it. Don't know if my info is current, but you can only deploy WinUI through their store. I just shorty looked into it, laughed a bit and went elsewhere. I have already left the MS stack behind completely.
I don't think Microsoft cares about dominating the PC anymore. Their continued efforts to make Windows user-hostile suggest to me that they don't want PCs to even exist. They want everyone using a locked-down walled-garden tablet OS and paying for cloud services.
The other players survive because Nintendo and Sony pour a lot of money into exclusives and have an extensive back catalog, but Valve isn't making exclusive games for Linux.