Big icons in QTabWidget are badly aligned (regression from Qt5 to Qt6)

When using a QTabWidget with big icons, these icons are extremely badly aligned in Qt6:

This seems to be a regression from Qt5 to Qt6. It used to work fine in Qt5:

These screenshots show the Fusion style. The same issue happens with the Windows style. So I suppose this is not a problem of a particular style, but a general problem. (I could not test with other styles, because Fusion and Windows are the only styles available on my Qt6 installation in Linux.)