Theming discrepancy between window decoration and application style

SUMMARY
When a Qt application uses e.g the Breeze theme, the window decoration and application style appear seamless. However, in some cases, the window content uses the style intended for out of focus windows while the window decoration uses the style intended for focused windows. I was only able to reproduce this issue on X11, but not on Wayland.

STEPS TO REPRODUCE

1. Use seamless theme like Breeze or one that has at least a noticeable difference in the application style between in- and out-of-focus windows
2. Open any Qt application, like Konsole
3. Click somewhere outside the application

OBSERVED RESULT

For a split second, the window decoration uses the out-of-focus style while the application itself still uses the in-focus style.

EXPECTED RESULT

Both switch at the same time.

OR

STEPS TO REPRODUCE

1. Use seamless theme like Breeze or one that has at least a noticeable difference in the application style between in- and out-of-focus windows
2. Open KDE's System Settings
3. Click on "Show more" button

OBSERVED RESULT

The window decoration uses the in-focus style while the application itself uses the out-of-focus style.

EXPECTED RESULT

Both switch at the same time.

SOFTWARE/OS VERSIONS
Windows:
macOS:
Linux/KDE Plasma: openSUSE Tumbleweed 20220825
(available in About System)
KDE Plasma Version: 5.25.4
KDE Frameworks Version: 5.97.0
Qt Version: 5.15.5

ADDITIONAL INFORMATION