This crossed my mind when I saw Iain's demonstration of Kubi-Wa.
Some believe that Seisan/Hangetsu is a close relative to the Four Gates (Zimen), a form ubiquitous in southern China as Sanchin. Here are some applications of the Four Gates from Eight Character Fist (also Zimen Quan). Anyway should there be no connection to karate at all, I would still find the demonstration of the "cheek to cheek" position interesting. At 0:53 you see the typical pinch/grab from Hangetsu.