I mean that a deadlift is just that...pick the weight up off the floor. Even if you rep it out, you can just drop it, reset, and lift again. Generally when people talk about lowering it with control and the ass not coming back, they're talking about ROMANIAN deadlifts which are the exact opposite of deadlifts. You start standing up, and bend over, the come back up...usually for reps. There is a very distinct, controlled, concentric and eccentric phase. In my opinion, they are far more "dangerous" than a true deadlift, for no other reason than it's harder to maintain the form that prevents the move from being dangerous in the first place.