Show Subtitle Tracks in Explorer Details for MP4

Adding the Subtitle Tracks column in Windows Explorer Details view shows what (if any) subtitles are contained in AVI, MKV and who knows what other video file types, but not for MP4.

Why? Why does installing this codec package add that for MKV and others but not MP4? Is there some special reason why not? Media Info has no problem telling if there are subtitles in an MP4, but that's much less convenient than having it visible right there along with Frame Height and Frame Width.

Details for MP4 files are handled by Windows itself. The Icaros PropertyHandler that the codec pack uses only supports a few specific file formats (such as FLV and MKV). Maybe in the future it will also support MP4.