Hmm, going by your logic, wouldn't the Bridge be just adjacent to main Engineering, and all on the same deck?
's argument was based on the relationship between the placement of the Engine Room to the adjoining corridor, and the internal layout that seemed to be indicated because of it.
Whether that was intentional or not on behalf of Matt Jefferies is of course freely debatable. However, using the physical soundstage to try and disprove it is somewhat wide of the mark. What next, insisting that Starships are made of wood because that's what the sets were made from?