...all communities named "piracy" are not the same, the full community name technically includes the instance, they are each their own "subreddit." You could subscribe to all of them if you wish, or to just "the largest one," but you can think of them as say "lemmyworldpiracy" and "beehawpiracy" and so on, they are just different communities.
It'd be like if two separate 15yo kids ran a fan page for their favorite anime character and expecting them to be identical simply because they are both about Goku, they're just different "sites" by different people, they just aren't the same thing simply because they're about the same topic.
Yeah that is annoying as hell. Like I get it if it's just like "my files are private, I'll open them if you have shares" but that whole "I need X album FLAC and a $50 baskin robbins gift card and then I might share with you" shit is the lamest thing I've ever seen.