One thing to remember is how quick it would be to build out maps in that era, big blocks to carve out the space and align/scale a single diffuse texture on each face.

I recall some anecdote from Harvey Smith that he liked to start the day earlier than the rest of the studio, and he could do a 'first draft' of a level before anyone arrived. I believe the example was the 'Ton hotel, which is a small map.