He's probably giving out his GV number and pretending his official number doesn't exist. I've just started doing this, as I didn't know how transparent "use GV for every call" really was.
Still, I don't think this is a hole in WP as much as an Android-specific feature.
Yeah, I wouldn't say the iOS implementation is really that great either. If you are that tied into Google services, Android is the only platform for you really. Google isn't going to just give away its best stuff onto other platforms, same with Apple and Microsoft.