Yes, only games, from the text of the change. This hints that perhaps the change is aimed at their attempts to implement parental controls and push into the child / family-friendly market? If using Google's system then they can enforce the controls on in-app billing set at the device level.

Of course, it is also possible that they recognize there is a lot of revenue flowing now from games through in-app purchases and have decided just to be anti-competitive assholes. But I would have to say, that has not been their form to date.