There is a legal concept that seems to be sadly lacking in the medical professions these days, called "informed consent." It means having the doctor or someone clearly explain things to the patient, and get the patient to sign off on anything that might be an additional charge, or to sign off on declining any tests that the doctor might advise that are not part of a basic appointment. Your doctor is not alone in failing to grasp the concept that patients don't like to be subjected to a bait-and-switch.
You wrote that you heard the office manager "tell the patient specifically that if doctor runs any tests, we would send them to his health insurance." I hope you understand that many people don't fully understand their health insurance -- and it's worse now, especially for seniors. I get my Medicare supplement through an agent. She's the sister of a high school classmate and I trust her completely. I haven't had the same carrier for two years in succession since I signed up for Medicare, because the companies change the plans every year. Your patient may not have understood about deductibles, or may not have know how close he was (or wasn't) to meeting the deductible.
My guess is that your office manager said "we'll send the tests to [your] health insurance," and the patient heard "Your health insurance will pay for the tests." IMHO, your office needs a printed form that spells out that you will submit bills to the patient's health insurance provider but that your office does NOT determine whether or not the insurance provider will pay, and that the patient is responsible for any amounts not paid by the insurance. The patients need to sign an acknowledgement that they have read this and understood it.
I think there should also be a form on which the doctor discloses any recommended tests that aren't included in the basic exam, and the patient checks a box to either accept or reject each recommended extra service. Yes, I get that the doctor is worried that he might be sued. If I were him, I'd be more worried about being turned in to the medical board for racketeering. If my doctor pulled that stunt with me once, it would be the last time he (or she) was my doctor.