That’s not really how this works. Right after a promo you’re not due for another promo. They are dividing a fixed size promo budget pie. So they rank you lower in order to be able to rank someone else higher. There’s no other reason, because it’s impossible to accurately measure engineer’s “performance”, or to even define it in the first place.

At Microsoft, for example, in the olden days at least, managers would keep around a certain percentage of deadwood on the team to give their best people good ratings and meet their firing quota if the need arises.