I think a false 9 drops deep on occasions and at times becomes sort of a #10, this is usually to drag centre halves out of position and leave space in behind usually for attacking wingers / inside forwards to exploit.
Whereas the job of a #10 is to create chances and take the role of a playmaker, more often than not with a centre forward directly in front. I think their role relies more on what they do with the ball i.e creating chances, while the role of a false 9 has a lot more to do with off the ball play (creating space etc). I'd definitely say Bobby is a false 9. Coutinho would be more of a 10