Based on your recounting of the Lender's request, it seems clear to me that your assessment is spot on, correct and appropriate. In training/supervising more than a few Trainees, there comes a point when I see it's appropriate to remind them that they are the ones whose opinion is the one that matters and not the Lenders or the AMCs. One needs to recognize that were an appraisal to come before a regulating body such as the state, you and only you are legally responsible for defending your conclusion/valuation and no one else. Again, from the facts presented, your initial assessment is correct, that is the "answer" to the HBU question is correct. If the Lender insists on including the second 13 acre parcel being included in the valuation, then "No" to the HBU question is correct. Stand your ground and do not allow them to brow-beat you into agreeing to something you believe is wrong. Do not let the tail wag the dog.