"is empty" or "is not set" not working as expected? Profiles not entering segment.

Hi folks,

I’ve just taken over an account and am in the process of consolidating 10+ lists into a master list, and to say it’s getting convoluted is an understatement.

I’m at the point of creating a newsletter segment per below. The structure is Master List > Newsletter Segment.

I created two test profiles who both entered the master list, but did NOT enter the newsletter segment. I confirmed subscription via the double opt-in message so it’s not that.

At the moment the signup forms are only getting first name and email, and a lot of profiles currently have non-existent “content preferences” properties, so I wonder if it could be the circled options that are not effectively capturing the profiles who should be entering? 
 

Help please, I thought I understood how this worked!