Only 1/8" of NM cable sheathing in electrical box?
In my state the inspector Shall cite the code to write a violation. Your electrician is correct there needs to be at least 1/4" of sheath left on the cable. This is to protect the wires from the sharp edges on the knock out type boxes and from the clamps on that style. My experience is inspectors don't like DIY home owners and pull all kinds of B.S. I recently moved to a diferent county and pulled some permits as a home owner, after the 3rd BS violation told him he needed to show me the code sections for each violation because the wiring was done by an electrician. He thought he was going to catch someone doing work on the side until I gave him my license number from memory let's just say he got very red in the face and after showing him my license he barely looked at the finish inspecton except for verifying the GFCI outlets functioned correctly.