Well, he said they are "roomies", and nothing more. If you're getting the hint of a relationship from that, well, I guess that's up to you, but I wouldn't say it's canon.
By the way, Papyrus doesn't necessarily have to be dead for this ending to happen.
It's mostly because he's willing to leave everything behind to be with her, banished in the ruins. Unless he's still free to leave any time. I'm sure even if the ruins were completely and permanently sealed, he'd still have a "shortcut" out.
Anyway, that's the only neutral ending I've done other than the forced one in my pacifist run. I don't know the other epilogues.