Spec link: https://drafts.csswg.org/css-transforms-2/#individual-transforms
This differs from the transform property, which is currently spec'd as applying only to transformable elements:
http://www.w3.org/TR/css-transforms-1/#transform-property
I think the "transform" and individual transform properties should apply to the same set of elements. For now I think that means the individual transform properties should apply to transformable elements only unless/until the behavior of transforms on other elements is specified.