After a user completes an R&U workflow task as the Trainee role of a document, the report creator cannot use Trainee equals "<Username>" filter condition to get the document assigned to the user.
The user belongs to a group, and the group is assigned to the R&U workflow task as the Trainee role. A Trainee equals 'Username' report filter can find documents that are assigned to the user directly. It does not find documents that are assigned to a group that includes the user.
The report creator can use Recipient equals <User Name> condition to filter the document.