Robert Comsol wrote:
"That ramp is a lot longer than I imagined! Interesting to find out."
I have my doubts whether this is really the case. Look again at the b&w picture, it suggests a rather steep ramp and looking at the videos the people in the background passing this area get shorter in a very short amount of time (hence my original theory of stairs). Additionally, the door behind the A-Frame seems to have the same distance to the A-Frame as in the rest of TOS, except that it has 'sunk' into the floor. And the distance to the door in the far background doesn't seem to be another corridor length.
What we see filmed isn't always the same as what we see behind the scenes.
In the behind-the-scenes BW picture, you can see that several "walls" are stacked close to each other and brought very close to the A frame and that they aren't very far down vertically relative to the A frame.
In the filmed corridor, those walls are moved further away and they are significantly further down vertically. Since the doorframes match up at those distances, the ramp is consistent as seen.