For drawings with dual "Document Properties / Dimensions / Dual Dimensions / dual dimensions display"  checked.

If you change the number of decimal places for a dimension that has been placed in the drawing.

Why is there not the ability to have a check box in the Document Properties area

Say under "Document Properties / Units" that says:

Change Secondary (Dual Dim) decimal places when modifying the Primary Dim on a drawing.

Then when I change inch from .000 to .00 the metric dim would change from .00 to .0