[kingston]

House map shows that there is plenty of unused space beyond the wall of doors... You can see in the cap from the tour that the staircase is flush with the wall... That being said there is nothing saying that a hallway can't pass though it under the stairs unless there is something the that structurally makes it impassable...

I'm not sure what these "people" you speak of are basing their information on... The only place the staircase does not extend to the wall is near the bottom... Where the door sits the staircase is flush with the wall... A hallway could easily pass through to a task room... Leaving the other door leading to the DR and there is more than enough room for it...