Words do in fact have meaning, which is why if you want your decision to be viewed as an insurance one rather than a medical one, you probably should avoid using phrases like "medically necessary" as justification for your decision to approve or deny insurance coverage. Using that phrase strongly suggests that while the ultimate decision was about providing or denying insurance coverage, what informed that decision was a medical determination about the actual necessity of the procedure. If you want to keep the decision firmly in the insurance realm, better considerations to mention might be expected lifetime payouts, shareholder value, and "because fuck you that's why".