At the end of episode 2, it was revealed that Cold Harbor is related to Gemma: https://hips.hearstapps.com/hmg-prod/images/severance-season-2-ms-casey-678a99b2d8acf.png?crop=0.7641975308641975xw:1xh;center,top&resize=980:*

I’m assuming this also goes back to the reason Mark has his glass cube - he was surprisingly fast when finishing a file related to Gemma, which is also the reason only he can finish her.