My understanding is that the content is essentially self-hosted, so content removed from relays still exists on the posting user's client and can be accessed directly, just like a website sending out RSS. So saying it "still exist on the network" is technically true, but only in the same way that you would say that about say bittorrent or the open web. What people host/post is present raw, what is amplified/"curated"/relayed is filtered. Client settings/config sets default and custom user content interaction, like a browser which can have adblock or not.

In principle, this seems like a decent solution, but I can see why different users prefer different protocols, differing to moderation takes a burden off of the user to vet inbound content. The same can be achieved via relays but the culture of "curation" seems weaker because the pressure from the userbase is lower to optimize it, as users are not solely reliant on any one relays. An odd network effect, but a truly invested curation/admin team could just as easily build a well "curated" relay as a well moderated instance.