wondering if faceboook’s promo system is the same as google’s.
At Facebook you don't write a packet self-proposing for promo like I believe you do at Google. It's up to your managers to decide on that around the time they do calibrations, which are done amongst a bunch of senior management and engineers.
Does this mean that if you're stack ranked near the top of your level you get promoted? Is it that simple?
No. You need to have sustained performance across halfs. If the top of the stack is extraordinary performance in absolute terms, that might imply promotion.
No.