Here is a link to 0801, which is the original announcement and is referenced in 0808
https://www.efanniemae.com/sf/guides.../2008/0801.pdf
"if another borrower on the mortgage is the owner of the tradeline".
This is not what the ECOA says, and looks like why the clarified with 0808.
If another borrower is not the owner, but the co-borrower has spousal AU accounts, then they must be scored.
I'm interpreting it to say if jlynn and her mother are buying a house together, and either jlynn or her mother have AU accounts, which belong to their respective spouses, then those lines must be scored.
If some lender interprets one of those announcements, without the other, some lender is going to screw up.
Regardless, that's going to leave some doors wide open, as they will have to inquire into marital status to make that detrmination.