Front and aft stairs are not synched, because they are chosen depending on the door's height, which is not the same so, if we tried to "sync" them, we'll might end up in situations where if we locked the choice from the lower exit, the same stair might not reach the aft door, or vice-versa, if we locked the choice on the higher exit, the front exit might be lower than the higher stair minimum height so, every door choose its stair independently.