Yes this EEE fear exists but I think it's unreasonable in my eyes. AP being managed by W3C is one reason for it.
Sure Meta will probably extend AP for their own use but it's not that they can simply decide that the new feature that they introduced and is at first only working on their platform is the standard from now.
I definitely agree that Nostr is something to keep an eye on but for me that's more about to see if there is stuff that works and can be introduced in AP as well. Because of all the arguments above I don't think we should all switch to Nostr now.