or do the really have these faults, but if they had investigated your claim, you would have kept quiet and let everyone think that it's a fantastic place (as far as you were concerned)?

Disparaging an ex-employer in the public, even if the ills disclosed are minor-- which in Google's case, they are-- can do considerable damage. Or it might not. It's hard to measure the cost of lost opportunity (in this case, lost recruiting). In any case, it's a move to take seriously, because it involves downside risk for both employer and whistleblower and the upside is quite minimal. It's not something to do just because you have a negative experience, because 3/4 of work experiences are pretty negative (by which, I mean they get less out of the job and the company than they should) for most people. If a company is going to get a public smear, it has to earn it.

If Google had done the right thing and investigated, then terminated the person, I probably would still have warned my friends about the death of "Google culture" but I wouldn't have leaked Perf and the death of 20%T to the public.