In general there's flaws with that book in how the producer as auteur is emphasized... It goes back to the old classic Shadow Morton / Phil Spector idea of the pop-svengali; legitimate in how those guys managed to personify a certain style of record they made, but forgets about the elements... In the Spectorian 60s pop (or the Johnny Franz team at Phillips for Dusty Springfield / Scott Walker if you want to bring it back to the UK) there's a myriad of elements... Musicians, Producer, Arranger, Engineers, and the artists in question, whether or not you'd prefer to put airquotes around whether or not a Britney or whomever is an artist.
Each of these elements are not drones, there's a certain degree of agency there... In the modern context, you have the songwriters, the co-producers who keep a Martin or Dr. Luke or whomever like figure hip... So for a record like Dr. Luke producing Katy Perry's "Black Horse", Juicy J was not only a guest rapper, but one of the assisting co-producers there because they wanted a modern rap sound and Dr. Luke is not like, in the clubs the way Juicy J might be. Benny Blanco, who's assisted a lot of Dr. Luke's music and recently now has become a solo producer working behind groups like Fifth Harmony did a collaborative album with Spank Rock waaaaay back when, so he has one foot in the more hipster worlds of electronic music and the other in the pop world (a position a Diplo has worked hard to occupy, though in his case with much more emphasis on branding himself as a producer artist rather than a background figure). Those co-producers occupy the 'musician' role often, now that organic music band structures are mostly novelty while the older establishment producers take the arranger role as described in the infamous "Since You Been Gone" analogy.
The thing is, in pop and also in rap/R&B this sort of 'pyramid system' has been long in effect... Timbaland had engineers who worked under him (such as Danjahandz) or writers (Static Major, Missy) who were occasionally featured artists on what he worked on, but primarily helped to refine who were the artists he had to work on. Eventually, they use their credits as 'parts' to further their careers, and that's what happened a lot in pop... Dr. Luke had Kesha sing on a Flo-Rida hook, the song did arguably well, and that's enough to convince the industry "OK the Kesha girl is investible". We recognize often that Aaliyah CHOSE to leave the more commercially successful R Kelly for Timbaland who was then kind of a still on the rise and not yet massively popular artist. Then after that, on the final album Timbaland is not present nearly as much, but Static Major as a writer is still very very much an integral part so he's getting moved as a songwriter into a more essential position while the 'beat-makers' are more or less disparate in reputation. You can claim of course management were integral in those decisions and maybe that was the case as well, but either way then the artist leads to that sort of shifting of the players behind the scenes of the record.
If anything, that's my issue with the book is that the Producer remains the unquestionable genius; there's a lot to be explored in the songwriters/affiliate producers, both those who remain behind the scenes figures and whom try to branch out and become artists in their own right. There's the boundaries of R&B/Pop in so much that, who gets to say Timbaland & The Neptunes can cross over into pop, but others can't. Why does rap, who do similar things much more blatantly now with ghost-writers and co-producers on beats, struggle with this sense of authenticity in the face of similar work. Who were the artists who drove their careers, who were passive? Even the sleazy aspect like, yes, did the Pussycat Dolls have that string of singles in the 00s b/c someone in the group was supposedly sleeping with Jimmy Iovine?
It introduces an idea that's been a sort of playpen for critics into the 'book world', but there's so much more to work with.