There is a method in KisPaintOpSettings. It is called ellipseOutline. It was added by Lukas in 2010. I guess, we wanted to add an ability to paint simplified outlines of complex paintops (there was something like that discussed at the sprint). This method is not used currently, and there is no option for it. We need to adopt it, or remove the method. The former, i guess, is better ;)
Actually, after that, we made a simplified but more accurate outline mode in krita's outline generator.
ellipseOutline is used for sketch, spray and deform brush outline. They use custom outlines. Don't remove it.
Okay, not a bug or wish then.