Let’s also not ignore the fact that these communities literally prohibit Links or content from being posted to them. So even if people make the Federation argument about cross-hosting it’s all moot in the end because the community doesn’t allow it in the first place.
Here is a link to the rules of the Piracy community you will notice if you have any form of reading comprehension (or if you actually read it and aren’t just trolling, like many people here) that rule 3 specifically prohibits linking to or hosting files, which many people making the federated hosting argument seem to leave out of the equation, likely because it destroys their argument altogether since their argument is about illegal content being hosted, but no illegal content is hosted in the first place (and any that is usually is removed by the mods for breaking the rules, just like it is here on Lemmy.world).