Well, I tend to disagree about this point. Qt is C++ as much as an ice cream truck is a truck - sure, it IS technically a truck, but that's where the similarities end. Qt basically reimplements every single C++ container and function with its own, has a slew of concepts that go directly against the current C++ trends (i.e. lots of pointers everywhere, CoW, ...), and on top of that it uses a preprocessor and also uses its own custom language to describe UIs (QML).

I am a professional C++ developer what happens to work often with Qt developers and I assure you, the skill-set you acquire while developing on Qt does not transfer at all to plain, standard C++, and vice-versa.