Hmmm. I do not what to think of this "discovery", but as a pathologist and former anatomist (and neuroscientist) I can tell you that the interstitium is a known anatomical structure in every organ (even in brain), but to single it out as a separate organ is in my opinion not warranted. From a scientific and diagnostic point of view it could perhaps lead to more focus and more grants coming into reasearch on the field of connective tissues in diseases. "Finding" new organs is popular these days, and recently the mesentery (https://en.wikipedia.org/wiki/Mesentery) was singled out as a separate organ.