It’s just about the starting items: Staff of Magic Missile, Cloth Armor, Ration of Food and 0/20 waterskin.
Only the food ration will be unavailable, but the sheep are long gone when you get hungry. Also throwing waterskin wouldn’t be an issue, but you’ll have to wait with collecting dews.
No, I can go on exploring the floor and then go to that room when I’m back at the entrance … or go there when I’m out of staff charges.
edit: No, I’m wrong. It only feels like taking longer, but the detour would take more turns. Unless I have to wait for my staff to recharge anyways.