Primary assignment swimlane for Autotask

For Autotask customers, there's a new swimlane for ticket and task boards for grouping by Primary Resource.

How is this different than the Resource swimlane? The Resource swimlane shows a ticket or task for a member if he or she is assigned as either the primary or a secondary, but the Primary Resource swimlane only shows work where the member is assigned as the primary. Tickets and tasks without a primary resource are shown in their own swimlane at the top of the page, even if they have secondary assignments.