Someone could have put some kind of "miracle additive" in their F'ed up engine to "cure" it. There are so many things you can buy to put into your oil that do nothing but spend money that there's no way to know. At this point, it doesn't really matter, the motor needs a complete teardown and rebuild anyway. You will probably find a reason when all the parts are on the bench. In any case, if that was mine and I wanted to fix it that's what I would do. It's pretty cheap to tear it apart.
I didn't watch the video first. But I think I am right. Miracle cure that the owner didn't know about or wouldn't cop to.