I don't think
Dave Barry has ever used "I am not making this up" when he really
was making something up. He even
addressed this in a
column. "No, I really am really not making it up," he said, when somebody asked him whether or not he really made stuff up and then claimed it as truth.
It's a shame real journalists can't be held to the same standards. (Okay, that's not strictly fair, but omission and inaccuracy, whether by ignorance or malice, can hopelessly skew any issue.)
Anyway, I believe him.