Using Qt5 binary release as kit with Qt6 build, Quick3D items don't work

Using Qt5 kit with Qt6 build, Quick3D items don't work. Warning appears to be that QtQuick3D 1.15 is not found, though this is against QT 5.15.4 binary release, so it definitely should be there. Designer specifics for 3D items are found, which also supports the fact that the module is actually found.

To repro, create a new Qt5 project and change the kit to Qt 5.15.4 binary release (create the kit manually if you don't already have it).

Same issue when using "Desktop" kit with snapshot release.