@lrhodes @gvelez17 @shiri @snarfed.org
If the bridge forgets about the block somehow, then the follow may be restored on the AT side if Eta's PDS pulls Delta's AT repository from the bridge to refresh/catch up after a disconnect and doesn't see the block, yes.
The bridge can probe whether Delta blocks Eta over AP at least if Delta's instance requires Authorized Fetch, so when possible, it should probably do that at a low frequency to keep its records straight.