Flat towing damage

In the Yamaha ATV warranty Policy paragraph 3, item i, says "the warranty does not extend to damage due to flat towing. (see your dealer for explanation)". What is meant by this, is there a possibility of causing damage when or if you must tow a Yamaha atv out of the bush to the trailhead?. Are there speed or distance restrictions for towing a Yamaha? Thanks.
Pat