"Formerly" my arse

What do they mean, "the singer formerly known as Cat Stevens"? Because, as far as I'm able to make out, they keep calling him that because that's all he's known as, all the time, ever. Because people just can't cope with that tricky foreign name he adopted, can they? They go all goldfish, confronted with that: what did you say? Garam Masala? Chicken Jalfrezi? Oh, Cat Stevens... Why didn't you say that in the first place?