Any idea what the "Calibration Assistant.app" useful for? It's not the normal display calibrator and it looks like to be used with hardware calibrators. I can adjust gamma and color toning/temperature.

The App is located here (OS X 10.11):
/System/Library/PrivateFrameworks/AmbientDisplay.framework/Versions/A/Resources/Calibration Assistant.app
It's designed for projectors/beamers (depending on the version of English used). It's not as correct as the one for normal displays, and designed for rather rough calibration of large uneven screens.