She argues that it's inaccurate to call them liberals because the term didn't exist then (at least with the same meaning, "liberality" meant generous) and they wouldn't have any idea what you were talking about. Basically, Anglophones retcon'd a rights-based liberalism in the late 1800s.

Personally, I think she takes the argument a bit too far. She credits Constant and de Staël for formalizing liberalism in the aftermath of the Revolution, essentially trying to save the good parts from the wreckage. But, like, Thomas Jefferson helped write the Declaration of the Rights of Man, which laid out the key principles Constant was trying to salvage, and he was most certainly influenced by Locke.

Still, I think this book is well worth reading as a corrective to the Anglo-centric, individual rights-based history of liberalism I've been exposed to in the past. There's a lot more to the story.