> The rules of film-making dictate that music documentaries require the artists’ consent.

Whose rule is this?

I guess you didn't bother to read the next sentence: "No access meant no rights to music, and no first-hand stories." 'Require' does not always connote a legal limit or even a necessity for permission, it can also mean that necessary elements are unavailable therefore making the project impractical or at least significantly harms it.

"No access meant no rights to music"

Nowadays often artists to not hold rights to own music. https://en.wikipedia.org/wiki/Taylor_Swift_masters_controver...