I have read it. If we don't take unproperly sourced and non peer-reviewed evidence in other matters, we shouldn't just because it produces an exciting story. The evidence for the switch is circumstantial at best, and relies on the fact that a French socialite swapped places with her 30 years younger daughter, and everyone who knew her kept quiet. All those hundreds of peoples. For 80 years. I don't want to revert to stereotypes but mind yer Chamberlain: "the French can't keep a government for six months, nor a secret for six hours..."
Never mind all the recorded and secondary evidence (the most any super centenarian ever had, because as the Usain Bolt of supercentenarians folk kept looking for that smoking gun in her life that even this research can't find) that supports Calment's age. The idea that dozens of people could keep a secret based around financial reward that long breaks suspension of disbelief given every year case like that ever.