Windows does not display the window owner in the Alt+Tab list. ROS does that. Also, if I call SetWindowLong (handle, GWL_HWNDPARENT, 0), Windows will display a window button on the taskbar. ROS - not. Also there is an error, if there is a button of the owner window on the taskbar, it must be activated/deactivated together with the window. Test app attached.
This issue relates to double app icons in alt+tab list for Delphi applications.