Don't think anyone said that. Or what I was saying, anyways. You can't deny that the elements associated with high functioning autism would help you be able to have a more single-mindedness when it comes to games, thus give you the natural ability to become good at games. That is, if games happens to be your focus. It's a dice-roll - being HFA may give you the natural "mindset" to be good at games, but there's a massive chance that you wont be interested in games. And, if you don't, you're not going to be good at it (same with everyone).
So no, just because you have autism does not mean you're going to be good at games. But, if you are a HFA and have an interest in games, it might.