Well, there is a difference between activating your "inner core" and the "6 pack" abdominals. The latter plays a pretty small role in stabilizing bigger movements relative to the TVA. The TVA won't get you a 6 pack, you still need to be working the rectus.
And to the OP, I don't think that the "push away" diet really needs to be something you necessarily need to worry about. The guys admits to being skinny to begin with, so it's not like we're dealing with an overweight man to begin with. You might do better getting stronger and gaining more muscle all over. Don't fall into the bullshit trap of just trying to get the 6 pack. It will leave you skinny and weak.