Ideas of how an examiner will look at this gets quite esoteric when comparing rents and what is below market. I doubt they will take an appraiser's word for it, although they may be considered a third party to the bank. Any idea what rent the appraiser was using for market rent? When he established the market rent, did he then take 80% of that number to determine the rent for low-and-moderate-income individuals to determine affordability?
But don't give up, since it is an LMI tract, maybe you can argue stabilization rather than affordable housing.
Societies that do not find work in and of itself "pleasing to God and requisite to Man," tend to be highly corrupt.