I'm very interested in this, as my POI also has this left-handed wrist action when arm moves forward. But...my POI isn't a family member, so that might only mean this trait is more common than we think, and so would not necessarily establish a firm connection to any one POI in particular.
If you can tell us at what point in the swatperp video you see this, I'd still be interested in taking a look.
Can you say which video you have seen your POI in action with left hand? If it's MSM. I understand that you cant, if FB. TY JMO