He was not a spy, but the gist of the Shaliah was a guy who claimed he was Charedi didnt eat Chulent, that sort of makes sense, not if if he was jewish. Someone who was brought up yeshivish should be expected to know Yeshivish customs
It would be no differnet if someone claimed they were Satmar and didnt speak any Yiddish or didnt know how to dress like a Chassid.