WorldServer - which engine runs User Assignments in WorldServer - the Background Engine or the Stats Engine?

Which engine performs User Assignments in WorldServer 11.1.x and later versions? They display the the Background Jobs page. Does it mean that they are run by the Background engine?

To improve the system-wide performance of actions related to user assignments, starting from WorldServer 11.1.1, project statistics such as assigned tasks or claimed tasks are now calculated asynchronously as background jobs.

However, the engine that runs those assignment jobs is not the background engine, but the Stats engine. This means that although User Assignments are displayed in the Background Jobs page with Job name Update assigned and claimed tasks,  they are always run by one engine only: the STATS engine. Increasing the number of background daemon will have no impact on User Assignments.

There is always only one Stats engine that runs User Assignments. There is also no way to configure Stats engines or daemon as you would do with Background Daemon.

This article might be relevant:

In a WorldServer 11.x environment, Users are not notified of tasks or project assignments and projects do not display in the 'Projects assigned to me' View