I was one of those people in denial initially because it's so random.
It looks like more info is rolling out and being released by NK themselves, including combat footage from the NK POV engaging the AFU. Depending on which source you cite, NK could of had anywhere between 6K to 15K troops involved in the Kursk operations. IMO, the casualty stat is real because NK troops likely participated in offensive operations but mostly played a supporting role to Russians.
Based on the combat footage released though, it seems like NK troops were well equipped and well trained, not much difference compared to Russian regulars.