I was an SDM at Amazon up until last month, I can tell you that the engineers are busy arguing over minute details and choice of wording in design docs. That's essentially the job.
You can safely say this for any user-facing product Amazon has. Look at the Prime TV interface, the Amazon Music app (and their "free" tier), etc. Everything they put out is third-rate, the only thing they know how to do well is AWS, which keeps the lights on.