function TCustomForm.GetFloating: Boolean;
begin
   Result := ((HostDockSite = nil) and (Parent=nil)
             and (FloatingDockSiteClass = ClassType)) <---------------
          or (inherited GetFloating);
end;

What's the reason for checking FloatingDockSiteClass here?

What can a form with no Parent and no HostDockSite do other than float?

DoDi