Why does create region tool (by difference) create disrupted XY plane projection when created with skewed view ?
Creating a region by difference with the "ACS Plane Lock on" produces a region which is a projection based on the CURRENT VIEW of the resultant region onto the XY-plane. Performing the same action with the "ACS Plane Lock off" creates a substitution of the second region from the first in the same plane i.e. a true region by difference.