@Lt. Washburn is correct - It took me a while to understand, but the Starbase section was built onto the stage 8 quarter / ten forward corridor. The corridor alongside the senior quarter was used as part (with a new red carpet), and the wall with the glass door and beyond all being new construction
I've done an analysis of the blueprint and the shot -
http://archive.frogland.co.uk/#15415366461389/16408123385193
I've overlaid the Starbase blueprint (
archive page) onto the stage 8 floor plan (
archive page), and then highlighted the corresponding walls between the screenshot and the plans. Also included is the probable camera position.
Now for the hypothetical - why did they do it this way?
- Originally the plan was to create a two story entrance on stage 16 (as shown on this blueprint - http://archive.frogland.co.uk/#15415366461389/15415373556778)
- The main costs that stick out are the two stories, the new lighting, and the four rounded walls (rounded always costs extra)
- They probably switched to the stage 8 version as it had two existing walls, part of the lighting in place already, and only one curved wall. Reducing costs and time to build.
- It is a short scene and probably did not warrant much budget - I think the large Pakled bridge took most of the allocated budget.
- Location shooting had its own costs and was probably simpler just to do this tiny corner of Starbase inhouse. Offhand I can't think of any TNG episodes with location shoots of interiors, just the exteriors.
- Alternatively more space on stage 16 was required for the Pakled bridge and the Starbase scene set had to be moved.