I think this is more "the rational way dentists interact with insurance companies". Insurance companies pay well under the usual market rate for treatment, so it makes sense for a dentist that accepts insurance to find a lot of problems that can be fixed in a short amount of time. "Yeah, that's probably a cavity" for 3 teeth on the same side of the mouth requires about as much time-in-chair as 1 cavity, but he gets to bill 3x. And since the insurance company is paying for it, there is no risk of not being paid. (It's bad for the patient, of course, because the fillings have to be redone in 10 years. But that ticking time bomb keeps the insurance payments coming in, and so it's good for everyone. Except the patient.)

My dentist doesn't take insurance and so he probably doesn't do this.