But I bet the author thinks a celebrity ought to be able to do something important and to do it well, and that vague conviction leads to the uncertainty of "semi-celebrity".
I saw a movie with Lindsay Lohan in it - "Mean Girls," a teen-chick flick. She can act like a teenage girl :-), and also sing, or at least she could a few years ago.
I think you're right about the point the author was trying to make.