tbf the hidden flag used to be less aggressive on the old site, you wouldn't see posts from it on the frontpage, but you didnt originally have to sub for posts to load up at all. it just never got changed as site upgrades happened. The early days of the site also had a very "everyone sees every post" thing going on and nobody wanted to use the subscribe feature (still somewhat an issue), so it was hidden just so it wouldnt be on everyone's frontpage unless they subbed.

worked fine early on but I think its ling outlived its usefulness since comm blocks are a thing now