It seems not possible to delete a hole within a face correctly while the hole touches the face at one point.
It does not work neither via SketchUp UI nor via ruby code.
e = Sketchup.active_model.entities
f1 = e.add_face [1,1,0],[8,1,0],[4,5,0]
f2 = e.add_face [2,2,0],[7,2,0],[4,4,0]
I have noticed this issue since SketchUp 2013