QT Applications don't respect window manager stacking settings

I'm using Linux with e16 as window manager with  focus follows mouse behaviour. The activated window will only be raised to foreground, if I choose it via Alt+Tab or click on the window header. If I put the mouse pointer into a window, the window gets the focus but keeps the stacking (background). This worked with every application so far.

Now I started using qtcreator. I noticed: When I click into the qtcreator window, it will be raised automatically to foreground. It doesn't respect the configured stacking. The qt designer behaves in the same way. Also brings the window into the foreground, when I click into the window.

I don't have a lot of qt-only applications installed. Afair Texmaker is also a qt-only application. In Texmaker the window behaviour works correct. The window raises only to forground by selecting via Alt+Tag or clicking on the window header.

In KDE (Plasma 5.55.0 installed) there are different stacking levels possible. The qt applications behave correct.