I've noticed that it helps on older style cars (American muscle in particular), I think this is due to the way older cars tend to have a separate body/chassis unlike modern cars where the body/chassis are part of each other. If you have a big heavy body flexing around on top of the chassis its going to act the same as suspension that is too soft and increase lateral body roll. With Strengthening in place the body shell flexes less and counters the problem.
Imagine a square cardboard tube, if you hold the bottom in place and then shake it the top it flexes from side to side, this is what the body shell is doing on top of the chassis. If you try the same thing with a piece of square plastic drainpipe it stays rigid, this highlights the effect of strengthening.
Hope that makes sense