[css-image] gradient midpoint vs color interpolation hint

CSS Images 4 defines the midpoint as a 'color interpolation hint'

Since we've always talked about that it specifies the midpoint of the
gradient and authors are more familiar with that term, can we change the
spec?
It's also a bit weird to call it a 'hint'

1: http://dev.w3.org/csswg/css-images-4/#color-interpolation-hint