@lpb and @Alex_Graniere,
Yes, exactly! I didn’t get that distinction at first, but that’s key to how this feature was designed to be used. As Joe Trollo expressed it in the API forum section:
The approval task represents your work reviewing some other task, and when you’ve reviewed it and declared it needs changes, your review is complete. (Later the task might be uncompleted to represent that there is new review to do, or a new approval task might be created and assigned.)