Not necessarily. I have some padded shorts that I use for public skating and they have a D30 insert. It's thinner than the foams typically used in impact shorts, presumably because it is more effective at absorbing shock. The foam in my Bauer helmet - the old 4500 that scores poorly - is quite thick, and much thicker than the D30 pad in my shorts. D30 is quite expensive, so that would add significantly to the cost of the helmet.
What strikes me (no pun intended) is that although the padding would spread the shock, it surely would have an insignificant impact (no pun intended) on the deceleration forces experienced by the brain. In other words, an unprotected head would on hitting ice suffer a shock wave and a deceleration. A good helmet would reduce the shock wave, but have little effect on the deceleration. I'd like to be proven wrong.
I must admit I do wonder about helmets. I play non contact hockey, but a week back when going slowly I had someone skate into me at full pelt, and I recall the sound of my helmet hitting his, followed by me falling backwards. I had a headache the following day. These bangs do concern me, and I'd happily pay more if I knew the helmet provided more protection from head injury.