Knee action - Pivot

How much does knee action, and to a certain extent "foot action" play in the proper motion of the pivot per TGM?

In 7-16, Knee Action it states

The amount of Bend will also determine the amount of Backstroke Turn and Down-stroke Slide

I think I understand Backstroke Turn but how does it affect Down Stroke slide? More flex the more slide?

It also states

The less Bend, the more the Pivot and Hip Slide will be restricted in both directions and the more upright the Plane tends to be.

The more upright the plane at impact? Does knee bend action during the swing tend to promote a plane shift? While knee bend allow of more pivot movement?

Does also the knee bend affect the plane angle? More bend, flatter the plane, therefore driver has more bend then wedge?