That's correct. Also nothing stopping either party from using their own keys if they prefer.

I'm just being a bit pedantic because a signed nostr message is essentially the same thing as a signed message from your node. Only the UX is different; it's not about there being an "account" from a technical or privacy perspective. it's that there's user friction in signing messages.

I think signing in with a node is essentially different from communicating via a randomly generated one-time-use nostr key By signing in with a node, you can send notifications to my account with confidence that I will see them the next time I log in, and you can log my sessions With a one-time-use nostr key, if you try to message me, I won't see the messages because I never sign in with that key again, and if you try to log my sessions, you'll only see one session