It's also pretty ridiculous their reverse proxy (ALB) "dual stack" mode can't serve IPv6 clients unless your backend app server is also IPv6. This is so much worse than anything you'd set up yourself.
Like most of the people in the linked reddit thread, I read the docs (and web search results[1] and LLM answers) as requiring v6 behind the ALB too. Not taking the poster's word for it yet but could be worth another look.