right, I am chinese and english learner there is no difference but(女人在闻着花 女人在闻话)these sentence reads smootherIn the examples you provided, I think there's no difference. They also can be expressed as
All of them(在做，做着，在做着)expressed the same meaning: someone is doing something.
However, there is difference depending on the context. More context needed (for instance, the grammar exercise you mentioned) to explain this clearly.