Some IOS apps not IPv6 ready?

Question

Apple requires that all apps in the app store to work in an all IPv6 network (no IPv4 network) according to this link

https://developer.apple.com/support/ipv6/

I was sniffing traffic from a few apps on the IOS and I checked to see if their APIs support IPv6 and it turns out that they don't. I checked their URLs on this site

http://ipv6-test.com/validate.php

I'm a bit puzzled about this. Aren't all apps in the Apple App store supposed to support IPv6?

One of the apps that I tested was the Textme app. Here is one of the URLs that they use within their app

https://api.textme-app.com/api/auth-token/

and by the looks of it, that domain does not support IPv6

Answer 1

The app needs to work in an IPv6-only environment with NAT64. That doesn't require the server to support IPv6, it just requires the app to not be bothered if the network pretends that the is reachable over IPv6-only.