I were never able to get setifactionary results with this because:
* In GTK apps new window is created from the same process
* OpenGL is single-threaded so performance per window is halfed
* GTK4 has problems with rendeing using multiple contexts resulting in some frames being upside down
So for the time being I am removing a non-working option. There is a chance
that it will be fixed and added in future, but for now lets not
advertise a functionality that does not work.
