There is, it seems to me, something right and something wrong with the suggestion that delusion and hallucination are helpfully seen as hybrid states between believing or perceiving on the one hand and imagining on the other.
It is helpful in so far as it steers us away from misidentification-based accounts - i.e. those which would have it that the hallucinator is imagining but mistaking their imagining for perceiving.
It does this by stressing that the conflation is in the states themselves and not in their apt identification.
What is wrong with it is something which I think the term 'state' also doesn't really help with. What is wrong is the way it overlooks two existential considerations. First, that the distinction between reality cognition (in perception or belief) and imagination is not just that between two separately individuatable states. For, I suggest, the phenomenon (and not just the concept) of imagination is defined as such in opposition to reality cognition. Only a being who can enjoy one can enjoy the other. When the distinction is instantiated in a human subject then that subject becomes both a perceiver and an imaginer. Before it is instantiated - well, say what you like but it's all a bit of a mush. Second, it also ignores the way in which the perceptual act not only defines an intentional object for itself but also defines a perceiving subject. Perception enacts selfhood - the self being constantly born, constituted, afresh as the subject pole in the subject-object perceptual opposition.
So, yes, talk of two 'states' which a subject contingently happens to be in does rather ignore the existential oppositional relations both between these two 'states' and between self and world in either perception or belief.
Another way of putting it: the suggestion is helpfully phenomenological, but unhelpfully un-existential. What we need here is a genuine existential phenomenology. Only in that way will we stand a chance of grasping the relation between severe ego-disturbance on the one hand and the psychopathological experience of the discombobulated ego on the other.