I suspect it does allow for design and distribution flexibility. I bought some of that sort of weight (and some tungsten-infused putty) for trying to add additional weight to improve the pulling power of a model locomotive. The putty's malleability and small size made it more amenable to fitting in the cast body.
Ideally with Pinewood Derby cars, you want to place the weight up as high as possible (in the rear) to convert potential energy into kenetic energy.
Tungsten weights are smaller, so the center of gravity can be slightly higher if you elevate the weights.
The product page says "Simply position the weights on your pinewood derby car and super glue them in place."
So if you're just glueing them to a standard model without elevating the tungsten weights somehow, they would actually be less effective than a less dense material, because the center of gravity would be lower.
If you did elevate the tungsten weights, whatever height that would match the top height with standard weights, the extra amount of energy would most likely be negligeable, and possibly lost due to variations in the track. Over a hundred races it would probably come out ahead slightly more ahead, but Pinewood Derby races are single elimination.
If one was sparing zero expense, using wind modeling software, etc for their Pinewood Derby, then yes, tungsten weights would be the way to go.
(I need to learn how to use wind modeling software now.)
