The cover applies, the damage pattern differs
A standard policy does not exclude unpaved roads. What changes is what goes wrong: undercarriage damage, punctured tires, windshield chips from loose surface and damage from striking debris. Most of that is collision rather than comprehensive, with the deductible that follows.
Recovery is not the same as towing
Roadside assistance limits are written around a tow from a road. Recovering a stuck vehicle from sand or a wash is a different operation at a different price, and policies frequently do not reach it. Knowing your limit in dollars rather than in principle is the useful preparation.
Where you are matters more than what happened
A breakdown an hour down an unpaved road is a long wait and an expensive retrieval regardless of the cause. That is an argument for carrying towing cover with a realistic limit and for telling somebody where you are going, rather than for a different policy.