Of course there is a curve in all companies. The question is of interpretation how review scores get assigned (stab in my back and lunches with manager's peers

Of course there is a curve in all companies. The question is of interpretation how review scores get assigned (stab in my back and lunches with manager's peers like in Microsoft and perhaps in Amazon), or based on a peer reviews like in Google. Besides, to the best of my knowledge there is no fixed bottom 10% (or any number of percents) in Google/Facebook which ought to let go after each review period, compared to Microsoft.