Window title bar not resizing correctly when using QT_SCALE_FACTOR

Description:

When running Qt5 applications in conjunction with QT_SCALE_FACTOR under GNOME, the width of the window title bar is not resized to match the scaled window content.

Steps to reproduce:

1. Open a terminal emulator
2. Run:
   $ QT_SCALE_FACTOR=2 <name-of-qt5-application>

Result:

The content of the window is scaled appropriately, however the title bar width does not match the content width. You can see an example in the attached screenshot.

Additional notes:

I was able to reproduce this issue with several Qt5 applications, such as: MusicBrainz Picard, KeepassXC, qBittorrent. However, I could not reproduce it with (for example) VLC 3.0.9.

Furthermore, someone suggested the following workaround, which indeed works (at least for me):

    $ QT_QPA_PLATFORM=xcb QT_SCALE_FACTOR=2 <name-of-qt5-application>

Note: I am not sure if the component I selected is appropriate for this bug report, however since I am not involved in the project development I made my best guess. Please correct it if necessary.