In case anyone is wondering, for curiosity's sake, the inch size was developed way back before the 90's when video cameras used CRT tubes to capture the image instead of CCDs. Tubes were typically measured in terms of diameter in fractional inches, but the useable area was only a central portion of the tube, so for any given size, a smaller center crop was used.
Since by the late 80's a whole industry was already built around the size convention of tubes, it made sense to keep it when talking about digital sensors, so a 2/3" lens could stay 2/3" and not some new made up figure.
I do wonder why NHK used such an outdated sizing method for a large sensor camera.