I would wager that the teeth of that saw blade are diamond impregnated. Due to the extremely slow speed that the blade is turning I don't imagine that heat build-up is a problem which would explain why there is no water cooling. Aiding that would be the wide gullets which would allow the stone dust/grit which is ground away from the cut to easily move away from the cutting point. Again, this eliminates the need for flushing the cut with water.

There was mention of the cut surface of the stone being slightly rough and in this I can see a last advantage in that would make for slightly larger stone dust/grit coming off of the cut, which when combined with the slow stone cutting speed would probably allow most of that junk to just fall down quietly within the saw instead of swirling around the operator in a lung-choking cloud.

Of course, this is all mere conjecture from watching the video.