They do remove content directly from relays. They claim they only remove content that is illegal to host, but I don't know how true that is, and there is always the risk it could change in the future.
I want the bsky org to be able to choose what content they host (and I think the internet would be a better place without section 230 protections allowing hosts to ignore the content they distribute); the promise as I understood it was that relays could be hot pluggable. If someone stopped carrying content (maybe it was illegal in /their/ region and not yours) you could failover to another relay.
However there is very little incentive to mirror any of the firehouse if someone else is doing it for free.
However there is very little incentive to mirror any of the firehouse if someone else is doing it for free.