FNMA Auth User Account

I have a borrower who, despite having a short credit history, has credit scores with all 3 bureaus. We are conventional and have DU approve/eligible findings. He has 2 tradelines reporting to credit, one of which is an authorized user account. The other one is an individual credit card which was opened 4 months ago. Both are reporting a clean credit history. My underwriter is conditioning for a 12 month payment history on the authorized user card, showing the borrower has been the one making the payments on the card. I’m dumbfounded. The guideline they continue to refer to is FNMA’s Selling Guide, B3-5.3-06, Authorized Users of Credit, which is a MANUAL underwrite requirement. We are not manually underwriting this loan as we have DU approval. Our bank does not even allow for manual underwrites on non-govy loans. To my knowledge and through everything I’ve read through the last week, as long as AUS is A/E and DU findings recognize the authorized user trade-line, no further documentation is needed. B3-5.3-09 states this verbatim.

Am I missing something here? I have a meeting with management tomorrow over this as I have been dealing with it for almost 2 weeks now.