How so? It is a large sheet of half inch of dense foam rubber (you probably don't realize how dense the padding is) with a hard plastic laminate over that. That is about as protective as you can get for the tailbone. I agree it isn't shaped the best for comfort though (hence why I use the Azzpad now).
The football one you linked to only has little quarter inch little soft foam nubs (more around the edge to try to deflect the impact a tiny bit)... because football players typically play on a relatively soft grassy field and rarely land on their tailbone. I doubt it will protect you much if you slipped out on your edge on a icy patch and slammed straight onto your tailbone. The link you had doesn't have a good photo of the tailbone... here is another link