No, the rationale is to allow people to block (more like mute, Lemmy-blocking doesn't really block) lemmy.ml
If !fantasy were to switch to !fantasy@lemmy.zip
- lemmy.ml users would still be able to access it
- users lemmy-blocking lemmy.ml would still be able to access it, and see comments from .ml users
That's an improvement over it being at .ml, where the second point isn't possible