It’s not just the differences in the chin, but the nose is completely different (left nostril higher than the right) and eyebrows, earlobes...
Here’s the link to the Youtube video in which Gilbert clearly identifies both the black and white images and the tinted images as being ANN DUNHAM.
http://www.youtube.com/watch?v=UMUlWbO1rhk
He obviously quite deliberately hasn’t named her by her full, real name, which is STANLEY ANN DUNHAM. But it’s the same woman none the-less...and she’s NOT Stanley Ann Dunham.