There is nothing cheap about buying a low cost dolly that could cause you to damage your car.
Damage ? ... how so ??
When you push the car and the casters don't pivot correctly and your car hits the wall or even worse another car.
But if this equipment does not operate as advertised- you simply TAKE THEM BACK for a refund
Not me. That hazmat suit is stuffy and hot. I'd just give them away to one of my West Virginia friends and go back to using a floorjack like I've done for 40 years.
If the results don't match the theory, change the theory.
