The reasoning behind this scoring is becouse this thing doesn't officially exist. It's not an OVA, but rather a preview for what could have been. Unless your a die hard fan of Project Moon's works, I reccomend not wasting your time on this. Since it may like me, make you want to curse the makers for not going through with it. Or like some other people curse them for wrecking the story even if a bit.
Either way, it's your call entirely.