vt7 dev release - Workflow Condition: Last Modified By (Campaings) fields

Create new Workflow and define Opportunity as Target Module.

In Workflow Condition block I see dropdown with all Target module and related modules fields.

But, I don't understand what's are "Last Modified By (Campaings)" fields. I understand Campaign Source - Campaign Details, Expectations and Actuals,... Those fields are related fields from related Campaigns to Opportunity module.

But "Last Modified By (Campaigns)" are not clear for me. See screens:

If I create the Workflow for Invoice module, the same fields are displayed even if Invoice module don't have relation to Campaing module.