Yes at one point nostr was unusable until strfry came along. If you get randomly put into a pool of unreliable relays then primal users will effectively rely on the primal caching relay for everything. Afaik all primal users have to use their relay anyways since it is used for pulling stats and stuff. I’m not sure if outbox even makes sense in clients that are centralized like this? It seems like a decentralized-in-name-only kind of setup.