I really dislike Coke products and in 2008 whenever I asked about options other than pop they started their response by telling me that I wouldn't get refills unless I ordered a Coke product. (I was always left thinking, "okay, but, since I'd drink about 1/4 of a Coke, the full glass of milk means I get more...could we move on and find out what you offer?")
My guess is that the new "single-serve" language is about keeping guests from expecting refills on milk, but, that they will still offer them for soft-drinks since a refilled soft-drink is still cheaper for them than a single glass of milk.
But, it could be a new cut-back.