Tumbler.currentIndex doesn't change when model is statically set

When set a static array-based model on Tumbler in Qt Quick Controls 2, its currentIndex doesn't work as user spins the Tumbler; shown value is changed on the screen but currentIndex remains the same.

Due to lack of test environment I could test only with Windows(Qt 5.15.0) and Ubuntu 20.04(Qt 5.12.8) and the test failed on both, but I'm sure that it would affect all the platforms.

You can replicate the issue with the attachment. If you change a value in one of the Tumbler it should change currentIndex and show a log to the console(e.g. "year.currentIndex changed". check line 45, 55, 72, and so on) but nothing will be shown on the console, and date(property of this QML component) won't change.

In this example the only thing where currentIndex is working as expected is day, which updates the model dynamically by Javascript.

Thank you in advance for your cooperation.