Wembleys a Woman? Well so is Bart, Arnold (from Hey Arnold), Bart, and Tommy Pickles so I guess thats not too far fetched...If she sounds somewhat like a man, I guess its not too bad an idea because the Japanese wouldnt know what our Wembley sounds like anyways....
Maybe it's because he has a high pitched panicky voice or they think they're being cute... It still seems odd to me. But then again, all Dub companies all over the world do the same thing. We gave adult Goku a MAN's voice, when he was originally played by a woman...