FB policy says they want to reward results and not effort. But it makes it hard to reward people for making progress on things that can't be done in 6 months.

It also makes for shitty service quality around the end of June and December, as people rush to push things to prod. (I've heard this may have changed, but it's hard to notice good service quality).

(Former FB employee)

It might be an interesting experiment to have each employee start their cycles (review cycle, or quarterly numbers for sales etc) on a random offset.

(This is what one should do with cron jobs so they don't hammer the server at exactly the same time.)

Compare https://en.wikipedia.org/wiki/Thundering_herd_problem

One wonders if this is why the train wreck of a web redesign was pushed out despite being... awful, and buggy as all hell.

Yes.