No, it’s not just about DRM, currently the storefronts do not guarantee continued access to the content.

For example, Valve can just close your Steam account at their discretion and you would no longer be able to log in or download any of your games

Not really surprising, Microsoft has been going a lot harder on the PC and cloud front, so it makes sense that their audience is split between those and Xbox, meanwhile Sony exclusives are only available on PS5.

It says right in your first link that it doesn’t support self signed certs