I can't help but get back to Mytran
's suggestion that the extended corridor ahead of the engine room (i.e. the forced perspective extension) is, indeed, a holographic display or a simple display screen / wall panel.
We are watching these decisive scenes at a stage, where not even the main viewscreen aboard the bridge has been activated
Thus, the simulation of an extended corridor could simply be another test picture at this stage of the departure preparations. IIRC we never see the extended corridor again once the ship is operational (and in TWOK this corridor ended where such a display panel would be).
I know, the turbo lift cab display
is a rough approximation at best, but I'm confident that the actual existing (set) part of the blue corridor is essentially a turbo lift lobby - and the holographic or display screen would indicate which turbo lift cabs would arrive next (left or right arrows) for anybody leaving the engine room.
If that were not the case you'd just be waiting in the corridor and would constantly have to look around to learn where to actually catch the next cab up or down.
IMHO, the turbo lift lobby idea is emphasized by
- Kirk entering this corridor from the port side on the upper level
- Kirk and Scotty running to the starboard side on the main level (ahead of the transporter malfunction scene)
Which reminds me to mention a quote from Roddenberry's TMP novelization:
"Montgomery Scott stood in the midst of what to many would have seemed pandemonium. The engine's intermix chamber, extending three levels above him and four more below, did not yet ..."
Is this still compatible with a vertical intermix shaft that runs up all the way into the impulse deflection crystal?