Perhaps you could elaborate on what credentials, exactly, one might need to be considered an authority on the medium?

Actually worked in the industry? Actually produced films. Studied the art for decades?

He is an authority. And he has expert opinions on the subject.

But at the end of the day, they're just that. Opinions, not stone tablets handed down by God. Although again, given his background, I will perhaps give his opinions a little more weight than, say, the average Medium author. ;)

And I don't thank anyone, except perhaps you, is claiming that those opinions constitute a monopoly on the subject.