CLIENT_FLAG_SKIP_TASKBAR and focusable window

We are currently experiencing unexpected behavior on xfwm4 and focus management. with this scenario:

• the program open in first the main window
  • the program open a second dialog window (with a property to hide it from the taskbar)
  • the second window open a third dialog window (with a property to hide it from the taskbar). When the third window is closed, the focus shifts to the first main window, while the second remain in the foreground, on top.

With XFWM code in focus.c, in the clientGetTopMostFocusable function, the call to clientSelectMask exclude windows with the CLIENT_FLAG_SKIP_TASKBAR flag from focusable window.

Is this intentional? Given that this behavior is not found on Windows or with Kwin. How to change/improve this behavior? Is there an option, or is a bugfix possible?