IIRC, the incorrect 1964 Lolo marriage date (as opposed to the documented (IIRC) 1965 Lolo marriage date) was on a passport document a decade later and could easily have been a “brain-fart.”
In 1965, there is no evidence that on presentation of the divorce decree from BHO Sr. the INS concluded there was bigamy, thus it would appear there was no evidence of bigamy by Stanley Ann in the Lolo INS files (not Sr. who was bigamous, IMO).
Maybe they didn’t pay close attention to the dates. As I said, a woman doesn’t usually forget her anniversary. The husband may, but the wife? Not usually.