I'd ignore the hyperbole in the article--and really, what does that have to do with the little girl? It's still very impressive for her to score in the 99th percentile--no matter what her age.
The article's take on why this is newsworthy is completely incorrect. It's newsworthy because they're letting 4 year old's into MENSA, not because the girl is somehow has the intelligence anywhere close to the adult members (which is what the article implies.)