Regarding your questions on incident metering as it applies to appears that you are relating from a standpoint of differences of reflective surfaces. That doesn't apply to incident metering. Light is light!!! Simple as that.

The degree of shadow may be variable to some degree in consideration of open shade or a darkened opening in a structure for instance. Thus if one were to orient the incident dome from the direction of the photographed object toward the camera lens to determine the highlight exposure and then again from a representative shaded position toward the camera lens the contrast can be determined. If the contrast range is greater then 7 stops the development would be reduced. If less then 7 stops the development would be expanded. If the contrast ranger were 7 stops this would be normal development.

I have the AE metered prism on my Bronica and would not find it applicable to controlled and knowledgeable exposures for my work.