If there's anything that I've learned over the years it's that you can have two seemingly related outages that are in fact completely unconnected to each other.
Doesn't seem improbable that a Google employee somewhere might have chosen to invalidate a bunch of tokens based on the cloudflare issue. There are 3rd party sites that accept Google account auth. Also not that big a jump that it wouldn't have been communicated well. Google doesn't always follow up with some kind of "what actually happened" postmortem either.
