More proof

  private static void Main()
  {
      Task.WhenAll(A(), B()).Wait();
  }


  private static async Task A()
  {
      Console.WriteLine(DateTime.Now + "started sync A");
      Thread.Sleep(10000);
      Console.WriteLine(DateTime.Now + "ended sync A");
      await Task.Delay(1); 
  }

  private static async Task B()
  {
      Console.WriteLine(DateTime.Now + "started sync B");
      Thread.Sleep(10000);
      Console.WriteLine(DateTime.Now + "ended sync B");
      await Task.Delay(1);
  }