This seemed implausible so I looked into it, and it's wrong as stated (at best, it needs to be made more precise to capture what you intended). First, you've mentioned Cloudflare, but the equivalent AWS product (CloudFront) does support TLS 1.3 (https://aws.amazon.com/about-aws/whats-new/2020/09/cloudfron...).
HN isn't behind CloudFront, though, so you probably mean their HTTP(s) load balancers (ALB) don't support TLS 1.3. Even that's an incomplete view of the load balancing picture, since the network load balancers (NLB) do support TLS 1.3, https://aws.amazon.com/about-aws/whats-new/2021/10/aws-netwo....