I see the ontological role of phenomenology as about establishing the qualitative features of consciousness. Certainly you can combine this first-person data with third-person data. That's how you get to know that the time-sequence illusion is an illusion. It's what we're doing when we try to locate neural correlates of consciousness.

But the potential for error correction ought to go both ways. If you can make a mistake on the basis of ideas derived from first-person observation, you can also do it on the basis of ideas derived from third-person observation. My thesis here is that people feel compelled to embrace certain mistaken conclusions about consciousness because of their beliefs about physical ontology, which derive from third-person observation.