I am surprised how wide door UL leaves for the AHJ without having any say-so about the qualification of the AHJ to perform such evaluation. It seems rather negligent to me. Maybe it will change after a legal challange.
Part of the 'problem' is that the UL specifications are relatively static and inflexible. UL 514B has specific requirements for specific fitting styles (i.e. cable, EMT, Rigid, conduit bodies, etc.). The tests are defined and requirements are specified. Comparing fitting field modifications to, let's say, a control panel fabrication, is not an apples to apples comparison. The panels, enclosures, or other similar category items are
designed to be drilled, punched, or modified in a way that they are to be used in an installation. The appropriate UL listing takes that into account.
In as far as fittings go, I can tell you that drilling holes in any conduit body (unless otherwise PERMITTED) by the manufacturer, will most certainly void the UL listing and the product warranty. If someone requires 'proof' that this modification is unacceptable, they should contact the manufacturer, who will give them the final decision on acceptance.
One final note as an analogy. We had a customer who received a red tag on an install. They had a 2.5" EMT conduit going into a 2.5" setscrew connector, which was then threaded into a Myers-style hub, which was attached to a panel. The inspector flagged the install because too many connector threads were visible outside the hub (i.e. the connector looked like it was only threaded 1 or 2 turns and not even close to bottoming out). Instead of reworking the EMT, removing the hub, and assembling the setscrew connector into the panel, the contractor elected to unscrew the connector from the hub and CUT OFF about 1" of thread and reassembled the fitting back into the hub (only 1 turn again). The fitting looked like it was screwed in more than it actually was. The inspector figured out what they did and flagged it again - this time for violating the UL listing. At that point the contractor realized that the right way was 1/2 the run needed to be redone. The inspector was very upset from that point forward. Our customer was upset with us for not backing him up with a letter stating his install was acceptable and still covered under the UL Listing...:roll: