Alphabet shifted the timing of stock compensation in 2017Q1, and this definitely screwed over some Noogler cohorts in 2017 (who may have expected a refresh in January 2017 or July 2017, but actually didn't get one until January 2018).

https://abc.xyz/investor/static/pdf/2017_Q1_Earnings_Transcr... (first paragraph, page 3)

Same at Facebook and Apple. At least, they're entirely formulaic.

That was not the case when I was at Apple- the formula recommended a bonus but IIRC it was officially at managerial discretion. Different orgs were run with different budgets, and while not this extreme I had seen similar things happen while I was there, including getting lower bonuses myself and one coworker quitting after their bonus was significantly lower than promised (or maybe they were denied it entirely, I don't remember exactly). We were told the same thing about organizational budgeting.

AFAICT (as a non-manager), it was entirely manager’s discretion, within a budget, at Apple.