Some web APIs don't need all browsers to support them for you to use them as a dev. I don't think FedCM not being in Safari or Firefox right now is a deal breaker for Bluesky or Mastodon. You don't even need to fully commit to the tech (Google doesn't even use every feature at the moment).
If you have a fediverse account, you can quote this note from your own instance. Search https://bsky.brid.gy/convert/ap/at://did:plc:ljlhzsoqytle2f4gdepkgibl/app.bsky.feed.post/3mcihkyjuz22d on your instance and quote it. (Note that quoting is not supported in Mastodon.)
💯, and this *is* the process through which web standards typically emerge.
A web API only works in one place.
Then another.
Then another.
And then we call it the web.
Or it doesn't replicate, and we don't.
RE: https://bsky.app/profile/did:plc:ljlhzsoqytle2f4gdepkgibl/post/3mcihkyjuz22d