hmmm… don’t know… as say’d … the values are delivered from graphics_card → driver → Windows (Taskmanager)… possible nvidia done somewhat different, as you mentioned you revervet the drivers.
Since the 30xx series comes out, I lost my believe at nvidia “a bit” 
Update: Taskmanager seems to decide what is to shown:
By default, the Task Manager will pick 4 engines to be displayed. The Task Manager will pick the engines it thinks are the most interesting.
… a AI Taskmanager