You are probably correct. However it does seem that a Presidential acknowledgment such as this is met to lend credibility to this "holiday".
Why interpret it as his intention to "lend credibility" to Kwanzaa? Why not interpret it as his desire to acknowledge a Black holiday and thus avoid being called racist--which we know he's sensitivie about? Until the "extolling the virtues" comment made earlier, I really didn't realize how minimally laudatory to Kwanzaa itself the statement actually was. It's more laudatory of Black contributions to society than it is of the holiday.