A literary agent's job is to sell an author. Obviously, Miriam Goderich thought Obama would be more salable if Kenyan-born than American-born. And Obama must have agreed, since he left the "error" go uncorrected, despite knowing the truth was out there. He's a compulsive liar.
Literary agents don’t sell their authors by lying about the most fundamental aspects of their bio. That is fraud. Plus the truth inevitably comes out. When it does the agent’s image is only slightly tarnished if he/she was lied to by the author, but is irreparably harmed if he/she knowingly lied and willingly participated in the deceit/false advertising.
It does sometimes happen that an author cons an agent into falsely promoting him/her on the basis of a biographical lie. I am unaware of any reputable agent that has knowingly participated in such a scheme/fraud. Acton & Dystel is an established and highly regarded agency. They would not risk the fallout of knowingly promoting a wholesale fraud. [The book they pitched to Obama was Journeys in Black and White, and had Obama’s Kenyan birth as its starting point. To base the entire book on a fraud is not consistent with Acton & Dystel’s solid, well-respected reputation.]
It still strikes me as an odd going-only-halfway measure. Selling an author" means selling books. So A&D pushed the exotic just as to the publisher but not the book-buying public? Maybe so. It's just not a convincing theory.
In any case, the Acton&Dystel bio card is always taken out of context (that being Obama telling the national media in 1990 that he was born in Hawaii) and badly overplayed. Though I suppose I understand the need of those pushing the Kenyan birth narrative to seize on it and not let go: if they didn't have the bio to waive, they'd not have much of anything.