Windows 10 native virtual keyboard doesn't pop up from a Qt app

When tapping on any of the following on a Windows 10 (or 7) tablet (in tablet mode):
TextInput, TextEdit, TextField, QTextEdit

the virtual keyboard does not come up (like every other text field in the system e.g. notepad, web browser...). This requires an alternate keyboard solution such as the Qt Virtual Keyboard when a native keyboard is available.

In Windows 10, the keyboard icon in the system tray (lower right) can be manually pressed to bring up the keyboard and enter text in a Qt field, but this is not required for other Windows applications (which bring it up automatically).

"Full Windows 10" support was announced in Qt 5.6, and I would have hoped this included use of the native keyboard https://www.qt.io/qt5-6/