Eric
The barrel and spine/shoulder tilt and barrel position is measured in Blast. You want a 90 degree angle of the bat going off the posture tilt. It’s part of the connection metrics, 90 degree at launch and 90 degrees at contact. I scored high in both in the swings I posted.
I don't disagree with that. Perpendicular to spine tilt makes sense for efficient movement. This would also be parallel to shoulder plane...in theory.