The Setup Wizard can use different platform dependent styles, see https://doc.qt.io/qt-6/qwizard.html#wizard-look-and-feel . On Linux the default is already Modern Style. For Windows a specific style was used, that didn't fit, hence the style specifically on Windows is already forced to modern style.

On macOS a similar situation exists, the system specific wizard style clashes with the layout of our wizard:

 

Use the modern style instead on all platforms