I'm sorry that it sounds like meaningless equivocation to you. Maybe you don't understand enough about how nostr works.

In nostr, to find somebody you look for their kind-10002 relay list. The spec says to spread that thing as far as you can. Relays are all supposed to host it if they support NIP-65. Just one per pubkey, a newer one replaces the older one. Inside that signed document you specify which relays you are using. At any time, you can change those relays and publish a new relay list document.

If you are using 5 relays (3 for outbox, 2 for inbox), then one of those outboxes decides to start charging, you go find a new provider, copy your data from the bad relay (or better yet one of your other trusted outbox relays) to the new provider, and update your relay list.

Instead of registering an endpoint in the DHT, and updating that whenever you like, you publish multiple endpoints in a relay list and update that.

Outboxes are where people come to read your posts. Inboxes is where people drop messages to you. Because I don't follow everybody who replies to me, I can't expect to see their replies on their outboxes, so they have to copy me on my inbox.

So in nostr you specify MULTIPLE relays. I'm not sure but with pkarr you specify one homeserver? Maybe you can specify many, I don't know.

BTW having multiple relays has problems. People go off and setup hundreds and then our clients get overwhelmed. I think the spec should say "only first 3 count".