> If they block that, they're blocking atproto functionality entirely, no?

Keep in mind, twitter got rid of their API. Google got rid of XMPP federation. Bluesky breaking or defederating atproto wouldn't impact most users, so they'd probably get less outcry than those examples.

https://support.google.com/code/answer/55703?hl=en

Yes, there are backup services that can help so you cannot be locked away from your data too.