I have my doubts that the sawstop technology relies on a ground path. Consider for example, a saw installed on a wooden floor, run by a full-clothed operator who may not be touching any metal part of the saw. It seems to me that there would not be a ground path for the circuitry to detect a current path. But the expectation is that if his hand contacts the blade they system would react.
I'm guessing that the lack of sensing technology is a compromise based battery life, physical size goals and probably price-point, though the saw's price point is pretty high.
As I understand it, all the sawstop saws use the same cartridge which is sized for a 10 inch blade, fitting one into this saw with its tiny blade may not have been practical. Engineering a cartridge that would be specific to the saw would likely add too much to the already high cost.
My thought is that with the sliding table feature, the saw is inherently safer to operate than many, and that if one makes use of the safety features available on it and follows good practice, the injury risk will be low. The risk is never zero, even on a Sawstop.
I do admit, however, that the lack of sensing tech is a bit disappointing for me, my intention this year is to either buy the new portable Sawstop or the Festool, depending on which attributes of either one win out in my decision process. I've had a chance to check out the Sawstop in a store, and I'm anxious to see (and hopefully operate) the Festool before I take one or the other home.