That'd be the one.
That's a new one to me, and it makes as much sense as anything, I suppose. The only reason I would tend to discount that theory is because travel options in 1963 for a single woman, 8+ months pregnant, would be extremely limited.
I think it's more likely she traveled back to the mainland when she was 5-6 months pregnant, and things developed from there.
Very interesting theory, though!
SAD may not have traveled alone at that advanced stage of pregnancy, and there’s a chance the birth was filed with the state of Hawaii, but not completed until later. It’s not clear if a birth record has to be complete before the birth is listed in the newspapers.