Yeah, good point. But what are these npubs? Aren't their kind:10002 relay lists not available? Sometimes people are s̶t̶u̶p̶i̶d̶ unwise and add thousands of relays to their list, we only try some of those. The next time we try we'll likely try different ones as internal outbox estimations change (see https://how-nostr-works.pages.dev/#/outbox for a glimpse of how that's done).
Discussion
The answer is no: we don't have a way to manage relays for each feed manually yet.
Oh, one way you can remedy that is by building an nprofile code for the person you want with the desired relays and adding that instead of just an npub.
You can do that easily with https://github.com/fiatjaf/nak -- nak encode nprofile (nak decode npub1... | jq -r .pubkey) -r relay.damus.io
Or with https://nak.nostr.com/ -- paste npub, click to add relay hint below (include the wss:// prefix).
TIL. I’ll give this a try. 👌🏻