It's basically a religious argument that realistically can only hold if there is something in the brain which violates known physics and allows for a category of computation that isn't just different, but different enough to be impossible to emulate within known physics.

Otherwise the brain can't compute anything a computer can't (eventually) emulate.

Maybe it's possible - as an atheist I find that near impossible to imagine, but I won't entirely dismiss the possibility, but I doubt it.