I don't think it is. His objections to the json library API can be addressed without introducing a single class.
He seems to want access to the internal implementation of converting bytes into a single Python object. That is probably just an internal function that can just be exposed. If he wants to override it from the top level, the library could permit that by just adding the function as a default parameter.
He wants it to deal with streaming. Python generators can help with this. The library could be refactored into implementing a json.load_stream function instead, which takes a string generator and returns some kind of object stream generator. The original json.loads function could be replaced with a wrapper around it for backwards compatibility and for API users who don't want the additional complexity.
None of this involves writing classes. A generator could be seen as a type of class instance, and one can implement a generator with classes, but generators have a well known and simple API which eliminates the need to define a new API, as the traditional writing of classes would do.
It seems to me that the writer has little experience of not using classes, so wants to solve every problem he has with a class. The API problems he want to address are genuine, but he's blind to any solution that doesn't use classes.
