1. First, I'm a bit baffled by some of the responses along the lines of "Amazon should just own their mistake". Sorry, but in the real world, "finders keepers" rarely applies (unless you're talking about crypto, but I digress...). I would certainly want a bug corrected if it were in my favor, and if a bug went the other way, I might need to re-evaluate my company satisfaction based on my new comp, but I have literally never seen a case of "sorry, payroll system made an error, but never mind you can keep it". It literally never works like that in any case, e.g. I work in fintech and if a bank accidentally deposits money into your account and you spend it, you can go to jail [1] - the bank doesn't say "whoops, our bad".
2. Many people who joined the workforce after the Great Recession have never had to deal with falling stock prices, and basically have just come to expect that the equity portion of their compensation should be like cash. The whole point of equity compensation is for it to be variable based on the success of the company. I get it, I wouldn't be happy with my compensation falling either (and I've certainly been there, in the .com bust), but I don't have much sympathy for folks who are just discovering that the variable component of their compensation can, in fact, be variable in the negative.
[1] https://abc13.com/spending-cash-bank-error-teller-error-can-...