When we started supporting video file reference for things like reaction videos, we wrote the spec to include Only allowed mime types are video/*., since all the supported videos had mime types like video/ogg and video/m2ts.

HLS video is a bit of a different beast, where the file reference would point to an index file that should have a mime type of application/vnd.apple.mpegurl, and would in turn point to a set of video files (potentially based on bandwidth or resolution). We should modify the spec to allow this format.