The point is that Google purposefully tried to keep the wages low. If not for FB, they would have never changed the practice. I have zero trust in Google for doing the right thing regarding salaries.
You don't have to trust in Google, only in self-interest. The reason FB broke the cartel is because they felt they could pick up some talented people by paying more. The reason Google normalizes salaries is because it negatively affects morale (and hence productivity & retention) when you have people paid dramatically different amounts for equal work. The reason big tech companies sponsor green cards is so they don't have to use up their H1B quota on you, and can instead get new H1Bs. They may not be doing it for your benefit, but that doesn't mean that you don't benefit from it.