You would have to declare that there's a mind in the first place, for it to be independent from the physical world would you not? The statement you made seems the same to me, maybe I misunderstood. If you accept a purely physical world and accept that the current model is the most accurate prediction of the world, then you accept that the mind cannot be distinct from our brain. The concept of mind then, although incredibly useful, has to be inadequate just as our current model is. Atoms, matter, energy are also very useful concepts but are inadequate and due to change. Because these concepts can (and most likely will) change, and because we each (as individuals) have a different concept associated with each of these word, it follows that they must be subjective.