If Cold Harbor was the pinnacle of their achievements, why would they only test that room once, when they tested other rooms multiple times?

I think the other rooms were gathering the data that Innie Mark was refining. They went to the other rooms multiple times to gather more data. Think like ‘training data’ for AI.

Cold Harbor was the test. That Innie Gemma was just about to pass the test before Outie Mark showed up was already showing they’d succeeded. If the test was for success, they achieved success. They wouldn’t need to test it again if Outie Mark hadn’t interfered. Even if they were planning on testing it with Gemma again, Drummond clearly already knew he could beat up Mark and kill him. Marks only sin was trying to get in a door, and Drummond decided that was enough for a death sentence. Which tells me they were already done with Mark.

Edit: I forgot to mention this. Lumon told us they were going to kill Gemma. They goat sacrifice was to be buried with a woman. Were there any other women the show told us were going to be killed? Not that I heard of