[Yoda]

Why would you reduce the downward?

The 'down' is 'Ball related' and in contrast to the Clubhead orbit achieved with a Square Plane Line. There is no deliberate attempt to reduce the 'down'in the Stroke itself. There simply is geometrically less 'Down' -- and more 'Out' -- in the Inside-Out Stroke (10-5-E) with respect to the Target Line. Similarly, there is more 'Down' -- and less 'Out' -- in the 'steeper' Outside-In Stroke (10-5-D). Again, these phenomena relate to the Target Line and not to the selected Inclined Plane itself.