thank you for bringing this up! Yes, you’re right—the hint is about finishing inside (it's preg ending). Right now, the game does force you to replay and doesn’t keep the gallery (If you not defeated the last boss).
Detail:
If you do it and get preg ending, it's will force you to make new game.
but If you get preg ending after defeated the last boss, you can get preg ending without forcing to new game.