These would not be strict clients according to the spec, so it's probably an anti-pattern and potentially a centralization vector, but it's happening and we can't prevent it. I think it will probably be ok as long as there is client diversity and people get used to moving between clients.
Discussion
How about a separate relay that shows the most popular posts from last 24h or something? Is that preferred? I think we could make that.
Yes, that would be great. I do want to see an app that allows one to browse relay global feeds kind like they were websites. https://github.com/alemmens/nuestr is going that way, but slowly.
I still think https://github.com/nostr-protocol/nips/pull/259 could help provide this additional second-layer functionality in a less-than-centralized way, without putting the burden of switching on end users.