Ok everything is awesome cool BUT the documentation tells me that I need give it "curve options".
Code:
luminancePlane->DetectEllipses(&ellipseDescriptor, &curveOptions, NULL, NULL);
The Vision Assistant helped me choose what I should set the values to in the EllipseDescriptor struct because it shows what settings it uses but it doesn't tell me what settings it use for CurveOptions and as a result, I can't make a CurveOptions struct and therefore I can't use ellipse detection.