If he made his conversion official, at list his betrayal will become obvious even to the demented Jews who might listen to him otherwise.
it would be official unless he denounced it.
it's easy to convert to islam.
we had a snooker player - ronnie O' sullivan, who said he was out with muslim friends, I think he went to a mosque, they told him to say something, then they were all really friendly he thought they were great. Next day he finds out he's a muslim!
of course, they didn't accept him 'cos he said he's not and he didn't know what he was saying!
But the assumption was that he is