Yechi, i differentiate between the two because if we look at learning nistar as we look at gemara, then almost no one is yotzei learning it, because it’s way above the hasagos of non-mekubualim. For everyone else, it’s as the taz lists it together with science and math, as chochmos.
If it’s learned as a tool for avodas Hashem, which was the hisnatzlus of many early chasidishe seforim(since it was forbidden to learn kabalah under 40, etc..), then it’s no different than sifrei mussar.