At which stage OpenGL goes left-handed?

Question

I know that OpenGL operate in right-handed mode in user space (in fact it don't care about in which system we work) and only goes left-handed after every user stage is completed. learnopengl says (emphasize mine)

Note that in normalized device coordinates OpenGL actually uses a left-handed system (the projection matrix switches the handedness).

However, I can't see how this statement could be true. With this simple example: let's say ModelViewProjection = Identity, the projection matrix does nothing so the final vertex is still right-handed.

If we test it, we can see that a an object rendered at a z = -0.5 will be hidden by another object at a z = -0.1, which should mean that that clip space is still right-handed, right?