ModenHttpClient issues

I am trying to use ModernHttpClient to replace the HttpClient. But I noticed some issues on Android and iOS platform. Not sure if I am not using them correctly and hope I can get some help here. The below code works well with HttpClient (using HttpClientHandler instead of NativeMessageHandler)
Thanks in advance.

The issues on Android:
I found even I set AllowAutoRedirect = false when creating the http handler, it still does the autoredirect.

The issue on iOS:
it failed to retrieved the cookies using the below code even I can debug and see the cookie in the response on iOS

The code like below :

 public async Task<string> Login(string EmailAddress, string Password)
        {
            var postData = new List<KeyValuePair<string, string>>
            {
                new KeyValuePair<string, string>("j_username",EmailAddress),
                new KeyValuePair<string, string>("j_password", Password),
                new KeyValuePair<string, string>("_spring_security_remember_me", "yes"),
                new KeyValuePair<string, string>("spring-security-redirect", "")
            };
            HttpContent postContent = new FormUrlEncodedContent(postData);
            CookieContainer cookieContainer = new CookieContainer();

            try
            {
                using (NativeMessageHandler= new NativeMessageHandler()  //using ModernHttpClient replaced Httpclient
                {
                    CookieContainer = cookieContainer,
                    AllowAutoRedirect = false,
                    UseCookies = true
                })
                using (HttpClient httpClient = new HttpClient(httpHandler))
                {                   
                    httpClient.DefaultRequestHeaders.Add("Accept-Language", "en-US,en;q=0.8");
                    httpClient.DefaultRequestHeaders.Add("Accept-Encoding", "gzip, deflate");

                    string LoginUrl = BaseUrl + "/j_spring_security_check_2";
                    var response = await httpClient.PostAsync(LoginUrl, postContent);

                    if (response != null && response.StatusCode == HttpStatusCode.Found)  // here on Android, i always http 200 instead of http 302
                    {
                        string token = string.Empty;
                        var responseCookies = cookieContainer.GetCookies(new Uri(BaseUrl));// here on iOS, responseCookies always contains 0 cookies
                        foreach (Cookie cookie in responseCookies)
                        {
                            if (cookie.Name.Equals("grails_remember_me", StringComparison.OrdinalIgnoreCase))
                            {
                                token = cookie.Value;
                            }
                        }

                        return token;
                    }                   
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine("PostRequestAsync exception {0}", ex.ToString());
            }
            return String.Empty;
        }  
}