About Implemented host name resolution with IPv6 in Unity 4.6.9 release-notes.

Hi, Unity team.

I have question about release-notes of unity-4.6.9.
It is "Implemented host name resolution with IPv6".

but, When I use "HttpWebRequest" on iOS9 device(Unity 4.6.9 build), I found the DNS error.
The error is "NameResolutionFailure".

I will teach a procedure.

1. Make DNS64/NAT64 access point on Mac.
   (https://developer.apple.com/library/ios/documentation/NetworkingInternetWeb/Conceptual/NetworkingOverview/UnderstandingandPreparingfortheIPv6Transition/UnderstandingandPreparingfortheIPv6Transition.html)
2. iOS9 device connect to access point.
3. Execute test code
   --------------
   HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create("Domain Name");
   webRequest.Method = "POST";
   Stream stream = webRequest.GetRequestStream();
   --------------
   
4. I found the error "NameResolutionFailure".

About "Implemented host name resolution with IPv6", will you tell me concretely?
and, Can you resolve this error?
Please tell me how to resolve this error.

Best regards,
Haruki