Google's final response was: "[we] have filed a bug [and] will [...] take a look", see my coworker (Jeremy)'s reply from May 6 at http://static.shubh.am/2fadisclosure/google.pdf
Clearly there was initially a simple misunderstanding/miscommunication. The reporter, on April 30, gave Google a few Australian telcos presumably vulnerable. But then he clarified on May 3 that it is actually at least "a large majority of telco's in Australia and UK" that are vulnerable. So, based on this new information, Google replied "Thanks for explaining the potential scope of this issue... [we] have filed a bug".
I mean, compare this to the way it was reported to Facebook: the reporter told them right away that 2 of the top 3 telcos in Australia are vulnerable(!) Now if it had been worded like this when first reported to Google, the misunderstanding would probably not have happened.