While the Gelugpa embraced the Jonang teaching on the Kalachakra, they ultimately opposed the Jonangpa (followers of the Jonang) over a difference in philosophical view.
For the Jonangpas, the emptiness of ultimate reality should not be characterized in the same way as the emptiness of apparent phenomena because it is prabhāsvara-saṃtāna, or "clear light mental continuum," endowed with limitless Buddha qualities [REF].