Alienating a fraction of that workforce will impact them, I think.
612k engineers. Let's assume that Amazon aims to hire the top 20% (I would expect software engineering skills to follow a power curve), so roughly 100k qualified workers.
That's pretty small if you're looking to employ 2-5k of them. That's a lot of competition given that there are likely at least 50 companies making Amazon-type offers.
I'm not saying they can't hire people if 10% of that pool decides they won't work there, but I'd imagine they would want to extend their pool to maybe top 30% at some point.
Amazon does a wide range of software development from robotics, backend AWS, internal software, and front end web development. So, most developers have relevant skills even if some positions are much harder to fill. That said their dev teams have many non programmers like systems administrators and testers etc so I suspect it’s closer to 2k US developers than 5k. As it looks like many of their openings are in Canada, Ireland, India, etc.