How do they know that an oral rinse product makes teeth 4x stronger?

A product called ACT® claims its use is for Fresh Breath / Stronger Teeth—and guarantees it makes teeth up to 4x stronger.

My question is, what kind of test can really determine this. One first might think of a hammer, or hammer-and-chisel. But how do they know that the same force is applied to both people’s teeth? (assuming one person has used the product and the other has not).

Is there some grinder or gestalt test used?