>Just to clarify, what should this update contain?

"We're working on it", possibly an ETA for a fix or some details. Technically it's fluff but people are not machines and the update is for people. We like the feeling that people are working on a fix, that people care and that the end is in sight. It makes the situation less stressful and, as for why Google should care, less stressed engineers won't bad mouth Google as much after the fact.

Compare Amazon's responses during their S3 outage: https://www.theregister.co.uk/2017/03/01/aws_s3_outage/ (toward the bottom)

What's the better communication plan: detailed, hourly updates or terse, one-line blog posts scattered across several days?

I think this comes down to the two outages being not at all similar. An s3 outage affects practically every Amazon customer. This affects a relatively small number of go customers.

And I'm confused about what was good about that response. That article is about how the s3 outage caused so many issues that Amazon couldn't update their status dashboard to inform users at all.