A pathologist is a physician, and therefore their final diagnosis and findings should be reported as the first-listed diagnosis. Although the intent of the colonoscopy was a screening, that code should be appended to the screening colonoscopy, not the pathologists' claim, since his tissue analysis shows a confirmation of a polyp. See AHA Coding Clinic 1Q2017.
The insurance company is telling the patient this because 1.) they aren't coders, and 2). their insured is upset because they are going to have deductible/co-insurance responsibility for the pathologist's bill, instead of a screening visit, which has no patient responsiblity. The payer is telling the patient that it was 'coded wrong', so that the payer won't have to take the heat for the patient being upset.
If I had a dollar for everyone of these scenarios that has crossed my desk since the ACA was implemented, I would be on a beach in Tahiti right now, sipping margaritas. It's a pain that the payers throw coders under the bus, when they don't even understand the rules.
We should not code for payment/coverage reasons.