Weird version numbers listed in Qt Quick docs

I spotted a strange versioning in Qt Quick docs. For example, in Qt 6.1 the KeyNavigation type says it needs QtQuick 2.1 (https://doc.qt.io/qt-6/qml-qtquick-keynavigation.html) whereas in Qt 5.15, the same type wants to have QtQuick 2.15 (https://doc.qt.io/qt-5.15/qml-qtquick-keynavigation.html) It is strange to see a lower number in Qt6 than in Qt5, despite of the fact that it seems, there are crazy 13 versions in between