Presumably this is still present in the encoded stream they decrypt. I believe the way around this is by prepaid accounts etc and throwaway emails. High end piracy like this is big business. Correct me if I’m wrong about the IDs in the stream though.

Edit: I just saw parents reply. It took a while to type this out on my phone :/

Sorry - clearly wasn't thinking straight - their alternative approach has this same issue (and having now read the article! - They do plan around this)