When using the Windows screen reader (narrator) to navigate through a UI, a QToolButton with a drop-down menu is only announced as "button". It is unclear, that clicking such a button would open a menu with additional options.
How to reproduce:
Use any Qt app with a QToolButton in it. Enable Windows screen reader via "Ctrl + Win + Enter". Then use the TAB key to navigate through the UI until you reach the QToolButton. Listen to what the screen reader describes. It say "XYZ - button", nothing more.