On screen scaling now has the following behaviour: -
As options are selected for a given image that increase its actual size, the image is scaled for best on-screen fit.
As options are selected that reduce its size, image size remains constant while the outer dimensions if the frame are reduced.
A frame visualised with a 4in mount will be bigger on screen than one with a 2in mount.
The benefit of using a larger mount (or frame) on a picture will be much easier for your customer to see now that it is no longer automatically scaled for best fit.