Relay hints come from keys, they are signposts (pun intended) where something is. That is a key-first approach, a hint you can trust if you trust the key. Nostr is in part a collective map of the internet. You found an event anywhere even from outside nostr, and from that entrypoint you can go furt...

Relay hints are key first because they are like signposts (pun intended) that show you a trusted direction where to go from there. Trusted if it comes from a key you trust. Hardcoding relays in apps is relay first approach. If I must know what relay to query before anything else, it is not optimal...