Bill Tindall
"For instance when a 34 degree blade angle is skewed to 60 degrees the effective blade angle is reduced to 18.6 degrees! "

I thought I had the mechanics of this situation figured out but the more I thought the more complicated I made the situation, correctly or not. I guess the issue is how the forces of the blade distribute between shearing across the fibers vs splitting them apart. What has become clear is that with the blade skewed some fraction of the force to cut or shear the fibers has been translated to a force perpendicular to the direction of the of plane travel(and wood fibers). A force in this direction doesn't lever the fibers apart to make a crack ahead of the blade tip. No doubt this has all been studied and reported somewhere with equations I wouldn't understand.

I expect an experienced planer takes advantage of subtle feedback of these forces, consciously or not, to adjust the plane to optimize these forces to reduce tear-out.