You mean when they separated internal infrastructure of the largest ecommerce in the world to the point when it was possible to sell it in commodified pieces to other businesses?

That is not what happened and is a fake myth origin story. AWS was started from scratch with a small team in south africa. The best description of all the myths and the real thing I've heard is here: https://www.acquired.fm/episodes/amazon-web-services

It sounds good to perpetuate the "but Amazon.com had extra capacity they could sell" but it's not true.

Unfortunately if the only source is this 3 hour podcast, you are going to have trouble convincing anyone.

There are sources, I didn't go through them yet, but they are there. It's pages of unorganized links, but it's something.

I think it's a bit unfair to characterize every company that is "starting" as a "startup", particularly when the "startup" in question is/was backed by one of the largest companies on the planet. I don't think people think of such companies' endeavors as startups, even when they are starting.

I mean... a little disingenuous. AMZN was a $10-20B publicly traded company at that time. When is it a startup vs a product offering of an established company?