Maybe. I can’t say either way. All I know is that the simplest answer is usually the correct one, Occam’s razor and what not. But even saying that, your theory could be close to the truth.
My theory was that it was "father unknown" or "bastard", depending on how Hawaii phrased it in those days, and the trouble started when the grandparents tried to manufacture a marriage for their daughter to give her little illegitimate baby at least the fictitious appearance of legitimacy. Hence the lack of a marriage license, odd newspaper announcements without any of the usual information, conflicting addresses, etc. Hence, perhaps, a quickie uncontested divorce without any inquiry into the circumstances of a marriage that never took place.
But it makes at least as much sense for BO's grandparents to have tried to get him the opportunity to "pass" as Caucasian, given the times and the scandal that would have ensued otherwise.
And of course that would have backfired more recently, although nobody at the time ever imagined in their wildest dreams that BO would be running for president some day, largely on the basis of his actual racial heritage. . . . .