I come across “sourdough” recipes with some commercial yeast in the recipe and just skip it (the Rye Baker is one source I use that does this). Timing [for me, anyway] is never exact or entirely predictable and I think @homebreadbaker has shown enough loaves that have gorgeous crumb and crust with very small amounts of starter (unfed at that!), i.e. less leaven might/will translate to longer fermentation times as will lower ambient temperature and a host of other factors.
The fact that it is legal in France (or anywhere), to call it natural leavened bread with a small amount of commercial yeast and that it is “traditional” in French artisanal breads is something that I did not know and seems odd.
FWIW, I did not buy the book: I have only looked at what recipes are previewed in the Amazon listing which are not all sourdough/natural leavened. I understand from the description and reviews that there is a sourdough section but commercial yeast recipes are in other parts of the book.
@homebreadbaker results are in comments for Challenging Sourdough Starter Convention
***edited … further thoughts @phillip, I think you “hit the nail on the head” with “unless someone intends to produce these loaves on an industrial scale”. Many of the popular bread books are written by bakers who DO bake on an industrial scale or at least in a commercial bakery. As such they need to turn out volume of consistent loaves of bread and so their approach will be different than the home baker. I think there are lots of things to be learned from commercial bakers and I enjoy reading and thinking about each baker’s approach and taking what makes sense to me for my own process, but I also think it is good to question the entirety of their processes … in this case, maybe the use of commercial (dry or instant) yeast.