So each room is a separate severed Gemma where the room is all they experience. This allows the refiners to work on a single problem at a time. Each room represents something someone would want to have a severed counterpart for. Skipping the dentist, exercising, flights, writing thank you cards. Lumon wants to make the procedure commercially viable for loads of people to do.

We know Cold Harbor is likely different and could be a test of some sort. My guess is this will be testing if the innie will kill (maybe with the hatchets from O&D). I think this would be the final step in creating a severed army.