If I understand correctly, your argument is:
"Parent says only members of the core Go team are known to be doing stuff with Go in Google. But that is circular reasoning on his part, because anybody who makes something in Go also becomes a member of the core Go team (or he considers him one, anyway).
I don't think it holds.
The core Go team is more or less specific and stable over the years, and the news about projects and stuff usually come from certain core members (Rob, Brad, and 1-2 more).
Very rarely do they come from other, random guys at Google (the YouTube thing being the exception IIRC).
So it's not like Google has mass adoption from tons of Google developers but he dismisses it because they all are "just from members of the Go team" in his eyes.
And, of course, thinking a language is excellent and using it in your project, by no means necessitates you becoming a member of said language's core team. We don't see much rise in the Go core team members anyway (if any).