[BerntR]

On the swing I used - the Power Golf swing - we look almost straight down the target line. The clubshaft is parallel to, and above the impact shaft plane in the down stroke and follow thru. The shaft stays close to parallel throughout. At the same time it seems clear that his hand path is outside-in

On the 5 lessons swing we have a bit different perspective. We look at the swing from behind and from outside the target line. The hand path seems to be straight down our view line. Camera position seem to be very close to the hand path plane through impact. The clubhead seems to be close to on-plane after transition and through impact, but then it raises high above it. The hand path is however above the clubhead plane after transition and then moves below it at and just past impact.

The down the line view in power golf seems to be more looking at the plane of the clubhead while the crossline view of the 5 lessons swing seem to be better aligned with the plane of his hand path.

I don't think this boils down to planar circles.