That would explain our experience. We got new insurance a few years back, and my wife scrutinized every bill and EOB form. She is a wonderfully detail-oriented person. Things would get denied for no reason at all, and she was constantly calling to get things corrected.
After a while, they stopped making mistakes. It appears of file has been placed in the "Won't take any sh!t" pile, which is a pretty good pile to be in!
Having worked in the health insurance industry for 17 years for big national companies and smaller regional ones, I can tell you this is BS. Health Insurance companies are tightly regulated by the states in which the coverage policies are written. In most states, medical necessity criteria used to deny claims must be scientifically sound AND approved by state regulators.
Any such policy of random denial would be quickly spotted by the regulators. Furthermore, there would be far fewer denied claims if physicians didn't instill unrealistic expectations in patients and order unnecessary tests.