Indeed, being on the top floor or not could reasonably be assumed either way. The two different staircases is basically the only option due to the circumstances.

As for no intention fighting on the stairs, that part would depend on if the enemy charged at us while we were still on them. My character, being nimble, wouldn't personally care either way. If she knew they'd be placed in such a circumstance she could rush ahead and block them long enough for Judgment to reach the top.