Yes, it's merely an enabled - multiple providers will still have to be interoperable. That's not as infeasible as it sounds, though. For some applications it is, but consider browser bookmarks: most browsers can read each others export files (perhaps they've already converged to the same one by now?).

Likewise, this might make sense for open source PWAs. They can now be developed without needing to provide a server, and can simply be hosted on e.g. GitHub Pages or S3. People can now serve different instances of it and people can switch between those.