Theres some truth around it. While QML may be nice I found the total experience of the QT stack lacking. It's still required to do large parts of the application in C++, since QML is mainly the View part. The impedance mismatch between the c++ and QML parts is huge compared to an environment that only uses a single language. I was part of some embedded system projects that used Actionscript (Adobe AIR) for some former projects and moved to QT in newer ones. For me personally it felt like a step backwards, from being able to implement the whole application in a single language with reasonable properties into a split world where I still need to use native code with all it's downsides. I don't want to say Actionscript is great here (it's for me somewhere between plain ES5 JS and Typescript) - I would also prefer a uniform Java or C# experience (as available on Android or Windows platforms) compared to a mixed C++/QML setup.

I see the main proposition of QT/QML in providing a framework that is not tied to a particular platform. The main thing that comes close are browser engines, but many people will find their huge footprints too large for using them for embedded applications (or partly even standalone desktop apps).