Let us take a five-acre parcel with improvements that are worth $200,000 and the land is worth $60,000 for a total of $260,000. Lender wants you to add a two-acre parcel for a total of seven acres. The two acres by itself is worth $40,000. If we add them up together as some would (wrongly) suggest the opinion of value is $300,000.
Now we have another argument that the appraisal be made with an HC that it is one seven-acre property. Just combining them together does not change the fact that the two acres is still excess land so this theory is also incorrect, but maybe better than the first. In this scenario the seven acres is worth about $70,000 (I am using land values from my market). So the value of a house on seven is $270,000. That is not the highest and best use as $270,000 is worth less than $300,000.
The misguided FNMA letter says the additional two acres is value in use. To me that says to value the whole property at $270,000 and that the FINAL value on the 1004 form would be $270,000 but that would not be the MARKET VALUE. The final appraisal value would be based on a value in use.
The correct way to address this would be to conclude a value of the house on five at $260,000 and do an addendum or a second separate appraisal stating the market value of the two acres is $40,000.