bidirectional one-to-one relation did not save child objects when constructor isn't used

Using your nose / face example for a one-to-one relationship, I created two classes:

class Face {
    static hasOne = [nose: Nose]
}

class Nose {
    Face face
}

What I expected to happen is when creating a Face object and assign a Nose object to it, both will be saved:

(1)
    Face face = new Face()
    Nose nose = new Nose()
    face.nose = nose
    face.save() 

This isn't working, but this is:

(2)
    Face face = new Face()
    Nose nose = new Nose()
    face.setNose(nose)
    -- *NEW* --> nose.face = face
    face.save()

And this (what I really don't understand):

(3)
    Face face = new Face(nose: new Nose()).save()

I don't understand, why (3) works as expected, (1) is not. It seems, that because of the bidirectional one-to-one relation the nose object isn't valid (nose.validate() => false), because in (1) I did not assign the face to the nose object, as in (2), but in (3) this is done automatically.