Those "raters" were contractors to the independent companies, and had no Google privileges at all. They couldn't come to campus and eat at the cafes, for example. They had no direct contact with any Google employees. I helped a relative get hired as one of those. This was about 11 years ago.
These outside companies had minimal oversight from Google, by design. My cousin joined the Search rater company and was given a test problem, which was timed and they had max times allowed. When she finished, they said "sorry, you took too long, we're not paying you."
I raised a stink and HR sent a representative to meet with the Search people. I sat in. The Search people were obnoxious little corporate toadies who claimed they couldn't interfere with any particular contractor's case, because of the legal separation requirements.
I so enjoyed watching the HR rep calmly and politely tell them, "That's great! Good job, you guys! But you know... when you hire someone and they don't do a good job, your remedy is to fire them. Not to refuse to pay."
She got paid.
I can't make any general statements about what happens to everyone, but in this particular case, I can't complain at all about HR's handling.