The OP demonstrates the heart of the SOW Rule. What is acceptable in one circumstance may not be acceptable in another. A buyer wishing to "validate" a potential sale price probably needs more analysis than a lender who is using the appraisal report as one piece of their risk assessment puzzle. When we do an exterior only appraisal we specifically state in the report that intended use is for evaluation of the loan, not validation of the sales contract.
Some still cling to the belief that all appraisals should be acceptable for all uses. Those appraisers are free to not accept exterior only appraisal assignments, and many do that. The truth is that all appraisals are based on a limited scope of work. No matter what you do, you could always do more.
The OP also demonstrates why the ASB said that "may rely" langauge on the Fannie Mae forms needs clarification. It could lead entities who are not intended users to think that they are. Entities other than the stated intended user can opt to use a report, but that is not the appraiser's intent.