'Evaluate As' field working in the All in one evaluations page

Summary:

Hi, in which scenarios is the 'Evaluate As' field blank and in which scenarios is this filled in with the logged in manager's name by default?

Content (please ensure you mask any confidential information):

We see that in some cases, the logged in managers name is automatically filled in the Evaluate as field in the All in one evaluations page. However in some cases, it is blank and leads to confusion on what the logged in manager should do. In which scenarios is this blank ??

Version (include the version you are using, if applicable):

25D Redwood

Code Snippet (add any code snippets that support your topic, if applicable):