For a function that says “Block everyone from <instancename>”, PieFed’s ability here does remarkably exactly and precisely what it says that it will.

In contrast, Lemmy’s “block instance” does not block either the users or domains (the term that Mbin and PieFed use to refer to URLs originating from an instance), and instead might be better termed a community muting.

Though so few people use PieFed (it’s not ready for mainstream yet) and so many here use Lemmy, that the “expectations” are stilted towards what Lemmy offers by default, even as misnamed as it is (although iirc the Sync and Connect apps for Lemmy can also do a true instance user block).