Complete example was added to Attachments (qvariantlist_bug.zip)

Consider following property declared in C++ code:

QPROPERTY(QVariantList values READ values NOTIFY valuesChanged)

This property is later used in QML: 

property var values: provider.values.reverse()

How I expected this code to work: provider.values is converted to JS array, reverse() method of JS array is called. It used to work like this until the update from Qt 6.2.4 to Qt 6.4.0 happened.

In QML debugger I'm able to observe that QVariantList is now converted to an object with string properties instead of Array of strings.