It means if you put size on any of the three your waste will get bigger, think abouit it, if you lower back gets bigger, your waste will get bigger, same with the abs and obliques.
I have to agree with this. Yes deads are a great exercise, but one can still develop a great back without doing them. There are plenty of other back exercises after all. I know lots of guys who have great backs, yet probably have never even seen a deadlift before lol.
I've noticed deads did make my waist bigger, which is why I ease off them and don't up the weight. Also, the tendency with deads is to keep going heavier and heavier and that can result in some inevitable back injury.
I have never found an exercise that gave me the trap development I got from deads....granted I probably have horrible genetics in that area I can shrug forever and never get the results...
Gotta agree though in other areas they are pretty over rated...I only realized this after not being able to do them for a long time