It really has more to do with thread patterns and how tight they are then trucks without mud flaps, especial those redxxxx trucks. Truck mudflaps need to be 18” or less from the ground, so a lifted truck will show more tire but also most of those trucks have wider tire grooves so most pickup very few rocks. So unless the mud flaps reach the ground or no mud flaps like on cars there is little to no defense against rock chips other then following distance.
I live in the windshield rock chip capital of the world…Alaska. Average windshield life taking care to avoid issues is 2 years. I have gotten more chips from cars then from any redxxxx trucks. I drive about 6,000 miles a month to include a dump truck and not one vehicle fairs better then another when it comes to getting windshield chips. Even as tall as a dump truck is I get hit and most times it’s from cars as they are changing lanes. i have done a bit of study of this to see about cutting my windshield expenses and looking at dashcam footage the rock is released at the road surface from the tire…..so unless the mud flaps reach the ground or are those special flaps that the guys towing campers use it will make little to no difference. And those one piece flaps or ones that reach the ground the rock just gets released to hit the flap and either goes out the side or under and gets a good bounce into the guy trying to hang way back. I can even say I have rocked my self…😝😜🤣