Of course, the irony of all of this is that they end up discriminating against the very people they need: The different, the strange, the quirky, the innovative - everyone who doesn't perfectly fit the criteria of a safe hire where nobody can criticize the hiring decision (and impact your promotion prospects).I work for Google as a software engineer and now also engineering manager.
There is no plausible mechanism by which a decision that anyone makes on whether to hire a candidate could affect that person's promotion prospects.
Interviewers don't make hiring decisions directly, they merely individually make recommendations to a committee that reviews these recommendations (along with other info like the candidate's resume). I have never heard of hiring committee "reporting" someone for recommending they hire someone "weird" or "bad" -- it would be kind of absurd. If you don't like the recommendation, don't take it! Similarly, hiring committee members are not going to be "written up" for making "weird", or "bad" recommendations. There isn't even a group of people who could plausibly do this.
There is plenty to criticize about how Google hires. But I disagree with what I read as the thesis of your post that we have to choose between a biased process and an effective one. Indeed the problem you identify is what I would describe as bias against people who don't fit a particular mold, people who are unusual or "weird", and so really what I think you're saying is that in trying to fight e.g. gender bias, we have introduced new biases.
I also don't think that's true. The counternarriative I'd propose is, we have always been biased against what we consider to be "weird" people, that's human nature. What we've been trying to do is change people's perception of what is weird, so that e.g. female or black coders aren't. That's what unbiasing is about.