QEvent::Leave is not sent when mouse leaves application window

On macOS (possibly Windows 10 as well) QPushButtons often do not receive QEvent::Leave events when the mouse leaves the QWidget application window.
This leaves the QPushButton widget in the "Hover" state until the mouse is brought over it again.

This is most easily repeated in a Debug build by putting a QPushButton against the right or left edge of the parent QWidget.

I have repeated this in Qt Creator 4.13.3 by hovering over the "Split" and "Collapse Pane" buttons on the right, though it is rarer/more difficult to do in a release build.

May be related to QTBUG-27478, which also appears to have reappeared in Qt 5.12.x when a QPushButton opens a popup