I think you misunderstood jordn's comment. When he said "staying in a job they dislike for another year just to get an extra $1k when they do quit." I think he was talking about a hypothetical situation were an employee has been working for Amazon for, say 2 years, and got offered the $2k. They'd be unlikely to wait another full year, just to be able to get $3k when they quit. In other words, if they want to quit, they will do so at the closest offer (e.g. $2k) rather than waiting another year AFTER that offer to get a larger one (e.g. $3k).
Of course it's likely employees would wait e.g. 3 months to get the "quitting bonus". In fact, jordn quite clearly stated that also, in the first line of his comment.
Right, I'm just elaborating and pointing out that this caveat only happens as long as the offer is structured in such a way that you have a massive increase to it at a specified time once a year.
Then if you hate your job and you're close to that specified time it's in your interest to wait, even though the point of the policy is that Amazon would rather that you quit.
If they just increased the offer with more granularity they wouldn't create that conflict of interest. You'd only get more money as a function of the time you stayed on the job, so you might as well quit right away instead of waiting a few months for a much larger payout.
Of course it's likely employees would wait e.g. 3 months to get the "quitting bonus". In fact, jordn quite clearly stated that also, in the first line of his comment.