It strikes me as interestingly analogous to what we've learned about how vision works (ie. virtually everything contradicts the naive 'well, the homunculus just sees image data as it comes in and interprets it accordingly' model, and it turns out that all kinds of specialized subsystems are at work, facial recognition, verbal priming improving the ability to distinguish stimuli against low-contrast backgrounds, all sorts of odd complexities).
The hallucinatory counterpart to the 'naive theory of vision' would be that when you hallucinate you experience false inputs on the video stream, exactly analogous to the real ones except not actually corroborated from your eyes. Since that isn't at all the case, though, and people hallucinate all kinds of things (albeit in a number of genres that do seem to be fairly stable), it suggests that you don't actually hallucinate the aliens, or the CIA mind control chips, or the demons, or the Air Loom; the pathological experience is something lower level, more affective, an intense feeling of 'malignant control at a distance' and then you end up doing your best to fill in (according to the tech level of your time and surroundings) the implementation of the pathological experience that you can't shake(I would imagine that this also makes 'treatment-by-refutation' essentially impossible: If somebody's belief that the CIA planted a chip in their brain, and that belief was the root problem, it might be possible to demonstrate to them that an MRI workup revealed no chip and they must be in error. If, however, the root problem is the inchoate feeling of malignant external control, trying to disprove one hypothesis or another about how that control is being handled is pure whack-a-mole. Even if you can talk them out of one theory, they still have something that cries out for explanation which you haven't even touched, so they'll be back with another one in short order).