Even if we had eyewitnesses to his birth, told in the first person, it would not have made any difference...........oh, wait, WE DID! His fraternal grandmother said she did!...................
That's the legend. It's a lot less clear-cut if you actually listen to the recording. We don't actually hear her saying it. There's a lot of confusion and people yelling, and the interviewer claiming that's what she said when it's not clear that she did. McRae keeps switching between "your son" and "your grandson" so it wouldn't be surprising if she were confused.