Your friend might be enrolled in one of the Insider rings. If you really want to verify it have your friend rollback his installation to 8.1 and see if his phone receives the WM10 update without being enrolled in Windows Insider. Again there hasn't been any official confirmation from anyone. In fact some of the posters here is the forums never came back when quizzed about their experience on the update which does make the whole claim kinda look fishy.