I suspect that may be better answered in the books. As far as I can remember, the previous three eyed raven could view the past, whereas Bran seems capable of actually affecting it. That's why some people are speculating he is actually the Lord of Light, because he can speak to the red priestesses gazing at the flames among other things. I need to do a re-read/rewatch so I could be totally wrong on that. It's all very confusing!