Entity filter using script not working

I am trying to create an entity filter for the Department table based on field values on that department's related CI records. (For example, departments with operational CIs.) Because this can't be done using the filter conditions UI we have created a script to do it.

The problem is that while the entity filter says it is getting the correct number of records it never actually populates the parent entity type.

A related oddity is that if I manually add the SysIDs in the same format that the script returns, then the "SysID is" filter condition returns zero records. If I use the "SysID is one of" condition the opposite is true. The manually created list returns the expected number of records and populates the entity type. If I use the script with this condition it returns zero records. Thus, the script generated list and a the same list that has been entered manually behave differently.

So... How do I achieve the goal of returning department entities based on a subset of their CIs? Is there something broken about the way script generated record lists populate entity types or am I just doing something wrong?

The only thing I can think of to fix this is to create a new table and use the script to populate it with the departments. The entity filter would then use that table to populate the entity type.