Not really. If you read his article carefully, you see that he bases his opinion on the fact that he was told Apple nog longer wanted to do October events. He expected an September announcement for a late October release, so he was kinda mixing both options into one.You're right, at his August 29 article he said that he didn't expected them anymore in September but if you look at his August 10 article :
"Interesting. I definitely expected them to be announced at the September event, even if they’re not available for sale until late October or early November. " (source : http://daringfireball.net/linked/2016/08/10/gurman-mbp)
He changed opinions, which isn't a fault or something. I'm just saying you shouldn't always trust the instincts/rumors of Gruber.