If the fixed lights are actually openable windows, it can be useful being
able to have a window ajar for ventilation without having the door open.

Although if this is done, care must be taken that the geometry allows the
French doors to be opened without smashing the open window. I imagine that
have the window and door hinges on the same post would be enough to ensure
this. As opening one would tend to close the other, rather than come across
an abrupt stop, especially if the window is unstayed, but held in position
by friction.

Christian.