No, Beehaw users posting in Beehaw communities visible on Lemmy.world. There's no third party interaction on either of those posts (just the Beehaw OP and Lemmy.world comments). Whether or not Beehaw is doing the convenience of sending updates, their content is accessible through Lemmy.world. It might take some action on a user here to trigger a pull, but it's entirely possible and you shouldn't expect defederation to prevent an intrusive instance from continuing to get content if they want it.

I don't know for sure there isn't some pathway through another instance causing this, but in my understanding that's not how federated communities work. There's the owner instance that has the true version of the content and distributes it around and then local copies on each other server that feed their updates back to the main instance. You wouldn't ever take a third party's version of a community because you couldn't trust its legitimacy.