This was regular stand-up sparring after the BJJ class. Not related to the class material at all. I saw one of the guys shadow-sparring while waiting for another guy to finish rolling, so I said (half-joking) "Want to do some stand-up?"
So we did. He had done some Tang Soo Do and kickboxing before, and he knew I had done AKK. It was just for fun.
The BJJ instructor is also a Hapkido instructor, so he didn't care.