The main problem with over-tightening a bolt, especially the size of a wheel bolt isn't that it's going to break, well not the first time anyway, but it's the stretching which over time and numerous over-tightenings could cause a failure due to either damage to the threads or metal fatigue within the metallurgical structure of the steel of the bolt.
Unlike many bolts used on a vehicle which once they've been done up they're unlikely to be removed again or if they are, it's maybe just once or twice, wheel nuts and bolts are designed to be fitted and refitted many times during the life of a vehicle.