No, the iOS requirement is for DNS64/NAT64. The server can be IPv4, the app has to work with an IPv6 address provided by DNS64. If 464XLAT were the deployed, the app could continue to speak IPv4, but it can't. Nothing to poster you replied to said contradicted that, so I'm not sure where you got it from that they speak about 464XLAT?
Maybe I misinterpreted the original poster's comment, my understanding was they were referring to IPv6-only carrier networks.
In the US (unsure about other countries but they may work the same), the IPv6-only carrier networks mostly (all?) use 464XLAT and not DNS64.
My comments are intentionally devoid of talking about what Apple's requirements are because I don't know then and as far as I know the other posters are correct there.