You need to pull the receptacles out of the wall or you don't really know how short the wires are after the installation. I suggest you try one of those 1.5 inch deep boxes on the side of an island - especially if it's a 20 amp circuit.

Does the "fist rule" work on 1 inch deep wiremold boxes too, or is that only 4 inches of conductor?

I've never heard of a written defect notice for wire length in a box. If I ever do, I'll start filing complaints when I see infractions. Our inspectors will welcome the extra work.