No, Dong does not refer to any Japanese styles, he's simply showing some elementary movements from his own system. But if it looks like a duck and it walks like a duck, then what the heck.
For Bill Reuter, sanchin was a breathing exercise. Period. Other than that, it was simply one and two and step and turn. Mr. Arakawa, on the other hand, would walk around trying to off-balance you. Sometimes he'd push hard; other times he'd pull ever so lightly. One time he would reap osotogari, another time he'd stop an apparently full-power strike to the stomach a quarter inch away. Almost aikido -- he'd see where the balance wasn't, and go there. For his part, Teruo Chinen walked around slapping you on the shoulders, whacking you in the back or stomach, or kicking to the inside of the legs. It was solid contact, but nothing like in Kyokushin Kai, where people seemed to think that sanchin was practice in being a human makiwara.
For what it's worth, Kanryo Higashionna reportedly had a trick where he invited people at festivals and sumo matches to grab hold of him, and then try to pull him out of position. Evidently he was pretty good at holding his place, too. And even today, sanchin can do fairly well at open tournaments, provided the person doing it has the upper body physique suitable for public display without a shirt. At one tournament I recall, a female bodybuilder took her jacket off for sanchin, just like the guys. She was wearing a halter top so that you could see the muscular definition, and the kata definitely drew the crowd. Got second, too, as I recall.