this is true to a point. But if you neglect abs but have an amazing diet, your abs will suck. Everyone I know, including myself, that has a good six pack works abs daily. I do anywhere between 120-300 crunches (different types) depending on my mood, and I think it works great. I know guys that do around 500 a day, and it definitly shows.
That said, if these guys ate mcdonalds everyday and didnt know what a vegetable was, they could do 10000 crunches and have amazing abs, but they'd be hidden under 2 inches of fat