That’s not true at all. I mean sure, if you’re going across a uniform height speedbump that’s wider than your car that might be true, and even then it makes a difference how close the low spot is to the suspension. The worst spot for clearance is halfway between the wheels if you’re taking speed bumps. But realistically, the ground you travel over is never flat, and the more stuff you have at that lower height the more likely you are to bash it on something. Especially if that thing isn’t parallel with the body of the car. You’re a heck of a lot more likely to snag that length of pipe than the point of a collector.
Low profile tires don’t have anything to do with it. My low profile tires are still taller than anything you could get stock. Overall tire height is what you have to pay attention to.