Yes, petrified wood is very dense, but the important point is that the ad noted that it is used for instrument making. In other words, it resonates like all wood. That's what makes wood good for things like violins, cellos, guitars, etc. And that's what makes wood tricky, but not impossible, to use as a stand or footer. If you wish to use the thing for vibration control, you can find more dense, non-wood materials locally. Although it would certainly be cool to say that your footers are exotic southern hemishpere petrified, prehistoric wood hand-crafted by Maori warriors, and therefore you had to pay $1000 for them.
Sorry, I got carried away there. No, I'm not familiar with the product, which was your original question. But I don't think it would be as good as other products you might find.