This is also the behaviour of the mobile site on iOS. I don't know what the mobile app is like but it sounds like it could just be a webview to the mobile site.

The website(mobile) does the same thing.

Is that interesting? Seems pretty standard and could even be handled relatively trivially in response to specific HTTP codes of any given individual request... Pretty sure nginx /whatever reverse proxy/load balancer they are using could do this natively without any special logic

It's interesting because of how awful the UX is there for a multi-trillion dollar company.

This would be acceptable if it showed an error notification after redirecting you, but it doesn't.

It just very cheerfully dumps you to their homepage.

It's bad enough the mobile app is just the website bundled up in a less functional form, the least they could do is add small things like this to it.

You should try hitting one of the potentially non-profitable customer filters. Like buy 5 things with a gift card that all ship to a different address on the same day.

No message, no warning, no email, just your password no longer works and then an endless loop of resetting and verification emails.

You'll find what you're trying to pay them for eventually if they put you back on their starting page — and they know it.

How does adding a simple toast-style message saying "We had some trouble finding that" alongside the homepage stop that?

Pretty sure they use CloudFront

CloudFront (and fastly) is a CDN which is very different than a reverse proxy or load-balancer.

A CDN is a reverse proxy with the ability to cache. They are not very different.

They use both Fastly and CloudFront.