I completely believe what happened on Garfield. Nobody (apart from the 2016 broker) bothered to compare the A properties to the B properties so they valued Garfield as an A based on the unfounded assumption that A=B. Which may or may not be similar on the purely accidental and coincidental basis.
As for the checkbox, I keep telling you; the checkbox works for me, not Fannie. And regardless how I checked the box I would proceed to clarify exactly what my opinion of HBU is in the report in a manner that nobody would be able to misunderstand.
As for the question of whether its OK to appraise a B property as if it were an A property, the answer is no - it isn't. However, it may be (and in that market probably is) necessary to use A properties as comps and then *consider and develop any applicable adjustments* that may be necessary to get to a supported opinion of the value of this B type property. That adjustment might be a "+", a "-", or an "="; I don't know, and I don't assume. That's an opinion to be developed, not an assumption to make.
No matter what, a "B" property is not exactly the same thing as an "A" property. Saying it is won't make it so, and neither will "Fannie will accept" make it so.