Partner has 850 credit score, dealer won’t consider financing

My partner is a financial nerd, and super on top of money. Their credit score was 851 via the dealer, and they got a letter saying “we only finance loans we can resell.”

Then their score is too high to get an interest rate worth reselling? Both dealer and secondary buyer don’t get enough of the piece of pie? Is that my takeaway?

Edit: the letter explicitly says the dealer can’t make money off selling the loan to a third party, and it’s not a tiny place it’s a huge and official Chevy/GM dealer.

ALSO: the salesman just responded to an email and said the letter is a glitch and it happens sometimes? A poster shared a link of a similar form letter going out to qualified buyers in CA. Weird. But the car industry is in a weird place, and the form letters are quite similar.