My classical station plays the better sort of movie scores - John Williams, LOTR etc - largely because the listeners approve of that kind of expansion of the definition of "classical music."
I used to listen to a classical music station that switched to jazz in the evenings. And I wouldn't mind if they started playing minimalism like Philip Glass, who certainly deserved to be counted as a serious, not pop, musician. (But I know the guy's stuff is not universally liked.)
For me, classical, jazz, minimalism and the best movie scores all fall under the same general category of "serious music." So I can easily see how someone might lump horror, sci fi and fantasy together without worrying too much about boundaries.