Not able to designate a Dormitory as Protective Custody

I recently acquired two Ex Law Enforcement prisoners, and I want to keep them from getting shanked. I created a larger cell with many amenities, which should take care of most of their needs except food. I have several officers deployed in the canteen, so I feel they are generally safe, but have not yet put them on permanent lockdown (as it feels more like a punishment than PC) so I'm trying to figure out how to do this. I assigned both PC inmates to this larger cell, but when trying to deploy it as a Protective Custody cell, the dormitory (the only way to have them share a cell) won't highlight on it's own. (See screenshots)

Screenshots:

This is the dormitory image in the regular screen (the showering inmate is also a PC inmate)

And here is the deployment screen, you can see that the dormitory is not selectable by itself without getting the hallway

Any help is appreciated.