The reason the lug nuts are swollen is primarily due to impact wrenches hammering them off and on. If they have done all the tire rotations tell them thanks. They all use impacts.
This is exactly the reason I hate taking a vehicle in for any type of repair. Even if the original issue is resolved another one is created by an inattentive person who worked on it. If you ever go into the service area of a shop you will see all sort of things that have been left off and most...