Nsec login definitely doesn't make much sense, aside from "bunkers are high friction for now so Damus users should just paste nsec". This will improve as bunkers improve, I will share a significant step forward in this area next week.
Local nsec signup makes total sense - let users start asap but then let them export nsec to a bunker. Nostr-login widget has this option built-in, only works with nsec.app for now but will be proposed as NIP upgrade when we are confident it's good enough.