ScrollView not update scrollbar handle position after data prepended to contentItem if handle is at the beginning

In the attached example model implements fetchMore() and appends new items in it. It is displayed in the ListView, which display items in revers mode, by using verticalLayoutDirection: ListView.BottomToTop. This is so-called "infinite scrolling", but in reverse mode: when the list scrolled to the top, the new items appended at the top.

If I quickly drag scroll indicator to the top, fetchMore() function of the model is not called any more, until I drag it somewhat lower.

To reproduce, run test program and quickly drag scrollbar handle to the top.

This does not happen with ScrollBar from Qt Labs Controls. Also, this does not happen on Qt 5.5.1.