With Enable Overprint (under Options), Graphics Inspection provides an on-screen simulation that approximates how blending and overprinting appear in color-separated output. Enable Overprint is enabled by default. When toggled on, it is applied to the inspection.
The Overprint icon at the top of the Preview panels simulates how blending and overprinting appear in color-separated output, but the simulation will not be applied to the inspection. It also re-loads the files.