So far, I've noticed that PlaneGeometry (Qt\6.9.1\msvc2022_64\include\QtQuick3DHelpers\6.9.1\QtQuick3DHelpers\private\planegeometry_p.h) is not exported. So the following snippet:

    PlaneGeometry {
        id: plane
        property int w: plane.width
    }

plus

set_target_properties(<target> PRIAVTE QT_QMLCACHEGEN_ARGUMENTS "--direct-calls")

is enough to cause an unresolved symbol build error because I am trying to refer to the "width" symbol.

Another example is "InfiniteGrid". It is not exported either, so

    InfiniteGrid {
        id: grid
        property int v: visible
    }

also causes unresolved symbol error. But unlike PlaneGeometry, problem with InfiniteGrid can be solved by explicitly binding to "grid.visible" instead of just "visible". On the other hand, PlaneGeometry problem is currently unsolvable. I don't know where the difference come from, but I think it is better to export all classes.