How can you tell it isn't?
Gotcha.
/s
But yeah, he really said that.
The simple fact that this thread is still open (OP never came back, but who cares right?) and people can just say whatever they want should tell you enough.
Ah, so it has already been asked. Well, since there are very little information available on sales, I would say that the willingness (or lack thereof) of developers to keep their games EGS exclusive might be indicative of general sales performance. If I was a developer and my game was selling well on a store that gives me a better cut then I would keep it exclusive to that store. If developers that signed on with EGS have become convinced that customers will indeed 'follow the games' then I would expect them to not release on Steam at all.