When appraisers are used, they often face revision requests from underwriters seeking clarification if their chosen comparables diverge from those preferred by the GSEs’ computer program, CU. This typically occurs when the GSEs’ algorithms suggest comparables closer in proximity to the subject property than those selected by the appraiser.
so, CU is advocating for whom, itself. although, as i have said before, CU comp choices can be head scratchers. the answer is simple. their stick is bigger than your stick. the lender doesn't need to ever use you again if you only tell them no. so somehow you educate them as to why that sale is not a comp. putting it into you report is not advocacy, it's survival. or in your case attach a letter to fannie in your handwriting that what they did is known advocacy and unethical appraisal practice when I see it, as you stated. all easy to exclaim, when retired. but i do respect your opinion & business decisions.
this profession has gotten harder enough without having to blow yourself up with the client.