They seem to be using radio waves instead of optical? Do radio waves penetrate the body or do they hypothesize that there will be changes on the surface of the skin due to blood sugar/pressure?
Yes, it is sub optical RF sensing. The important factor here is that the gluclose blood capacitively couples to small sensing antennas. The sensing antennas are resonant elements, whose exact resonance changes depending on the surrounding environment, in this case gluclose in the blood. You can then transmit an RF signal to the antenna, then record the signal reflected from the antenna’s port to estimate the gluclose level.