There is no water damage showing through, and the ceiling is smooth drywall. As for the white, it is mildew best I can tell. The water appears to be minimal leakage over time, and the insulation looks like it is compressed directly below, leading me to believe the water generally gets absorbed in small amounts and dries out. The seller was clueless, and as a mortgage broker he felt that he shouldn't have to repair anything a "certified FHA appraiser" didn't note on his appraisal. I convinced him otherwise and he is providing repair credit at close.
I am disappointed that the appraiser didn't note anything and rated it so well. I will see if I can drop the inspection report and appraisal in a drop box if anyone is interested in seeing and reading for evaluation. I really just want to feel somewhat vindicated by professionals that I am not crazy in assuming this is a subpar appraisal. I have no issue with the valuation.