It appears that the # of of reviews showing in the product review statistics is misleading. I have 1 review for an item with 3 variations and it shows that I have 3 reviews and asks me to respond to all three. Not sure what would actually happen if I did comment to all three.
Does look like it is possible to leave a review on the parent ASIN and then it only shows up 1 time in the statistics.
It would be great if it only showed as 1 review either way.