The Severed Floor is Mark's Harbor from the Cold

All the rooms that we've seem Gemma enter on the Testing Floor are about offloading unpleasant episodic experiences to an innie so that her outtie doesn't have to experience them, e.g. a dental visit or a plane ride. But what about more hazy chronic unpleasant feelings, such as longing and grief, that involve memories scattered throughout her lifetime? The testing floor that Gemma is on IS Cold Harbor itself. The 'unpleasant experience' that they're experimenting and gathering data on is Gemma's longing for Mark and the life that they had on the outside. Her outtie itself is the one that's being tested.

We know that Mark took a severed job at Lumon because he wanted to spare his innie of the grief that he experiences as an outtie. The severed floor is quite literally and figuratively a harbor for him from the cold (both from the cold weather outside and the cold feelings he has). But his outtie himself is still miserable. The Cold Harbor file is probably about refining the chips to a point where you can selectively delete a specific person or category from your memories, be it in outtie or innie mode. This is the reason why all those Gemma and Mark flashbacks are prominent in the episode, because it's about selectively deleting their cherished memories of each other from their minds.

It's also the reason why it took this long for Cold Harbor to pop up, since Lumon needed enough time to let Gemma and Mark's grief/longing for each other simmer so that they can collect data to refine from them. Likewise, this is probably why Cobel seems to be obsessed with Mark and Cold Harbor, since she empathizes with his grief and yearns to selectively erase the memories of her mother, who she seems to grieve for (or traumatized by?), from herself.

Cold Harbor is about death, but it isn't about avoiding experiencing your own death. It's about how those around you can avoid the unpleasant feelings associated with losing you.