If users land on 

https://doc.qt.io/qt-6/qtqml-tool-qmltc.html

or on 

https://doc.qt.io/qt-6/qtqml-tool-qmlsc.html

they cannot return to its parent page 

https://doc.qt.io/qt-6/qtqml-qtquick-compiler-tech.html

where the above two topics belong to. So the user has almost no chance to learn more about this topic, since it is not possible to see what is related

PS. I suspect that the actual qdoc page does not use breadcrumbs statements, and the qdoc compilation just generates some default ones based on the location of the qdoc file.