A year before the Acton & Dystel pamphlet was produced, Obama gave interviews to both the Chicago Tribune and Chicago Daily Herald in which he stated that he was born in Hawaii.
Now, these publications obviously circulated widely around Chicago. The A&D pamphlet, by contrast, had Obama's pithy bio among a group of 80 or so authors and was distributed just to a relatively small handful of publishers. In addition to the Chicago publications, the "born in Hawaii" reporting in 1990 was done also in the New York Times and Washington Post.
It doesn't seem likely that the A&D "born in Kenya" statement came directly from Obama, given that in interviews to these major national publications Obama the year earlier stated point-blank he was born in Hawaii. What would have been the motivation for stating it differently the next year? "Born in Hawaii" was already on the public record and circulated widely. And if the motivation was somehow to create a buzz around his forthcoming book, then why not include "born in Kenya" in the book itself? Or at least put it on the dust jacket? What would Obama accomplish by just putting it in this extremely-small-circulation agent's pamphlet?
The explanation that the bio was simply something cobbled together by someone at A&D makes more sense.