Take note of the language starting at the bottom of p.2 of the CFPB/DOJ publication indicating that Reg. B is not the only consideration. There have been claims on behalf of DACA recipients under 42 USC 1981, The court rulings in some of the cases cited in the footnotes of the CFPB/DOJ cases show that while it might not violate Reg. B to exclude all non-citizens, that doesn't mean that such a policy is permissible under 42 USC 1981.
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Nobody's perfect, not even a perfect stranger.