No more than an instance on Lemmy can make it so blocked a counts can't reply to someone who blocked them. That's just contradictory blocking philosophies at play.
The way that the defederation claim was originally made was that Piefed automatically blocks lemmy.ml, hexbear, and lemmygrad and automatically repopulates those instances as blocked if an instance owner wipes their defederation. This wasn't true. And lemmy.ml has never been on the autoblocklist.