I watched a cool video that covered this/the history of wall coverings not too long ago! Been a few weeks, but I think that old style involved horsehair mixed with plaster that they basically just slopped onto the walls.
If you’re interested: https://youtu.be/oepbuBGHEHM









Sounds like the game wasn’t exactly finished. Plus its just one project they finished at a studio, they could certainly have used the employees to work on a different new project.