I want to believe this as much as anyone, but I can't.
I mean, Polyphony Digital didn't reveal the game at E3. It's odd that they could reconcile the fact that although they are in a position where they could show it off whenever, they don't know when they will show it off, and actively chose not to at E3. If that was the case, that would be an bizarre decision from a business standpoint, considering the sim racing competition is more intense than ever, and GT7 is currently missing in action.
All the information he has given is vague, too, in such a way that neither proves anything new and concrete, but doesn't conflict with what we know so far - in short, it could be entirely true simply because it's so lacking in information. Your source has basically said:
'GT7 will be incredible, but it wasn't shown in that Bugatti trailer. It wasn't shown at E3, either, but it might be shown soon."
You don't need to be an insider or secret contact to be able to say that, because I suspect that's the view of GT7 almost everyone has now from what we know.