Agreed. The tagline talks about any programming language, and then the classes section goes on to talk aout classes, abstract classes, class hierarchies, etc. To me it seems like "any language" in that chapter at least would refer to what people traditionally call object oriented languages.

Lisps, some low level c-style languages (go and rust among the newer ones), and some ML languages with algebraic data types don't really have the same object orientation abstractions as Java, C#, and Python. Further more the class system in Javascript ES6 are a bit special.

It would be better to talk about domain modelling, suggest interesting domains to model, without actually specifying any particular way to do it.

Edit: I must add that the author have done a great job of collecting these suggestions for tasks though!