An agent isn't going to say what is and isn't specifically covered in a hypothetical claims situation. That opens them up to errors and omission claims potentially should you come back later saying Joe the agent said it was covered, here is the email. The insurance company can than stick it back on the agent.
Ambiguity is the name of the game in the insurance world.
Taking your vehicle on an off road trail where the likelihood of damage increases significantly vs road use against overall miles driven is a big change from what a standard policy was designed to do. We are the minority vehicle owners after all. With that said, insurance does cover stupidity so if you go offroad I would run with comprehensive/ full coverage on anything of major value and our lj's are right on the edge of value line IMO.
Coverage for things that occur offroad happen all the time. Some accidents that start on the road don't involve any sort of damage until the vehicle leaves the road. Idiots dunking their trucks at boat ramps, farm vehicles damaged while farming, construction vehicles, etc.
I would ask what are you trying to get covered? If you paid to wheel I think it could be argued under the competition clause. Outside of the policy comes case law in your specific state and what that state has defined as competition or reasonable off road use in a coverage decision case if one exists.