The body is a 50:50 talc:ball clay mix, it is very smooth and slick so the only particulate is from the grog. In this case the grog addition is being used to make the body resistant to thermal shock failure (for use as a flameware). The body itself is not low expansion nor are the grogged particles. But the sheer quantity of aggregate particles and their size creates an open porous matrix that makes it difficult for cracks to propagate. Of course lots of burnishing, an engobe or a thick glaze layer will be needed to make this surface functional. We could call this the "crow-bar" approach to flameware.
Flameware is ceramic that can withstand sudden temperature changes without cracking. The low thermal expansion of true flameware makes craze-free glazes very difficult.