'Win probability added' has been around for sometime already in baseball, is a good descriptive tool (altough not so good from a predictive point of view, but who cares), it's great that somebody started to calculate it in cricket. Then there are also the win shares, but it's a bit more difficult to work on that concept
However, we have another variable to take into account other than the score, which is time passed in the game; it's not the same to get in, or out, at 22/4 in the first or last day, but that'll be for some other time.
Another thing, as we have 3 (4) possible results, I think that there should be also a DRAW probability added (or lost), which of course should take into account time passed in the game.