Very interesting video! The idea of someone writing material for the artists is nothing new of course, we've all heard of the Brill Building in New York, but he's right that more people should be aware of the writers behind the hits.
Begs the question whether some of the hits would have been as successful if performed by other artists- what if Britney had been assigned I Kissed A Girl, instead of Katy Perry? If I were to ask this man for one of his unreleased songs, but together a crack squad of unheard of session musicians and record it, would we reach number one? I doubt it... the music business is, and always has been mostly a marketing exercise.