nobody is refusing to offer their sevices on linux because it is vulnerable
That’s not quite true, though in that case it’s about the service provider being unable to verify that the user isn’t running a operating system configured or modified to work against the interests of the service provider.
It’s probably more fair to call its claim of being decentralized fake or disingenuous. There doesn’t seem to be any way to participate in the ecosystem without going through the Bluesky relay, a central point of failure with strong incentives to eventually do something shitty.