With the caveat of not having read the book, and merely looking at the blurb, I’d say neither nor. The idea that musical notation is a shorthand for actual practice, that the ways people read that shorthand change as practice changes, and that the way the shorthand is applied in newer texts changes, following the changing way of people reading the shorthand, is not groundbreaking, at least not in performance-practical research of the past, say, two decades.
To my mind, it’s the methods of how principles like this one are applied to certain topics that set one research approach apart from another in terms of quality. One would have to look at the book itself, though, not the marketing blurb, because nobody knows who wrote that stuff. I surely didn’t write the blurb to Beethoven the Pianist, for example.
Just to pick an example about methods and goals out of my own bag of research, my performance practical chapters (about the so-called “common” touch and legato, and about trills) in my mentioned book (coincidentally also published in 2010) revisit some evidence and past arguments and provide my (hopefully better, or at least better understandable) argumentation around these topics. The historical record being what it is, however, one needs to accept the option of inconclusive outcomes because of knowledge gaps (one classic is our uncertainty in every single case we try to understand a historical tutor on performance issues in music, about the level of proficiency of the intended readership and about whether the book is predominantly prescriptive or descriptive), and of conflicting historical practices in times of stylistic and socio-political change (like in Beethoven’s time). Even if some of my own conclusions around Beethoven’s trill starts, for example, may seem “revisionist” to people who have learned to play them in another way, it would be silly to push that angle for reasons of standing out, and to claim that I’ve found “the answer”.
Final answers is not why we do research, and any claim to having found them smacks, if not of poor methodology, of a relative lack of knowledge. Why? Because the deeper one delves, the more one is confronted with the certainty that one knows too little to be able to provide single unequivocal answers.
Now for the practical musician this is frustrating, because we can’t sit on stage and play a trill in multiple ways simultaneously (just a silly example). We need to make choices. But for an author to dish out some pre-chewed “results” is a shortcut, and (as Stuart points out with the example of the half-tempo conspiracy theory [btw. it’s Winters. Not Wenders ((also: how did we even get here!)) ]) not always a very good one.
Whoever writes about performance practice should take the pedagogical task of the work more seriously than the potential of their work to be marketed as never-heard-of-revolutionary: this involves trying to strengthen the ability of the readers to understand arguments, to follow a critical interpretation of sources, to learn not only that but why they may agree or disagree with the author, and finally to make performance decisions on their own on the basis of that ability.