Something bothers me about the conclusion of the review...

"In this theory I treat the historical work as what it most manifestly is: a verbal structure in the form of a narrative prose discourse. Histories (and philosophies of history as well) combine a certain amount of 'data,' theoretical concepts for 'explaining' these data, and a narrative structure for their presentation as an icon of sets of events presumed to have occurred in times past. In addition, I maintain, they contain a deep structural content which is generally poetic, and specifically linguistic, in nature, and which serves as the precritically accepted paradigm of what a distinctively 'historical' explanation should be." (Hayden White, Metahistory, p. IX)

What MacKenzie Bezos points out, albeit in a localised fashion, is what the Humanities have come to regard as the "linguistic turn" during the course of the 20th century. As Hayden White states above (in his concern with historical writing), historical writing takes a certain set of data that is then fitted into a wider narrative, alongside some underlying meta-narrative, which marks a certain interpretive paradigm (e.g. a progress-narrative). This, in turn, means that no account can desribe "historical truth". It also means that every account is fundamentally literary (or, as he formulates it, at least linguistic). It is no surprise, then, that the Bezos biography does not describe "historical fact". However, it also means that a biography written by Bezos's wive or even his autobiography cannot describe "historical truth" either. Every account remains a narrative, and thus fictional, even if based "on real events", as Hollywood so neatly calls it.

Hayden White continues: The chosen (or, in this case, criticised) writers' "status as possible models of historical representation or conceptualization does not depend upon the nature of the 'data' they used to support their generalizations or the theories they invoked to explain them; it depends rather upon the consistency, coherence, and illuminative power of their respective visions of the historical field." (Hayden White, Metahistory, p. 4)

So her final claim is dubious, at best: "Ideally, authors are careful to ensure people know whether what they are reading is history or an entertaining fictionalization. Hollywood often uses a more honest label: 'a story based on true events.' If authors won’t admit they’ve crossed this important line, their characters can do it for them."

While the "character" may certainly give you their version of the story, what they present is far from being "historical truth". They also choose examples, omit others, pick and make decisions, depending on their very own narrative. This is less a clash of "fiction" versus "historical truth", but instead a clash of two narratives. The character's narrative (in this case, Bezos's) might carry more authority (he is the character in question, after all), but the account remains nevertheless a narrative, which can also be criticised.

This is the same reflex as can be observed sometimes with old guest listeners at universities who torpedo (especially) historical lectures with a simple claim: "But I was there in 19xx, and I didn't know about or notice any of that." And while that might be a true data point, it doesn't mean that it somehow invalidates the wider narrative.

Edit: The author can thus certainly criticise the overall narrative or narrative thrust in the biography, but pointing out singular data points that simply oppose a given data point do not serve the same function.