Embedded WebVTT Subtitles?

Are embedded WebVTT subtitles supported? I’ve created an MKV that includes a subtitle track of this type, it plays without problems in VLC, I can turn it on and off, but opening the file in Infuse on my Mac, it doesn’t even acknowledge that the subtitle track is present, let alone let me use it.

I’d prefer to stick with embedded, keep life simple (yeah, I know, doing OCR to convert PGS or VOBSUB to WebVTT and then doing assorted things with mkvmerge to add the track to the file isn’t actually that simple) - I’m not planning to use downloaded subtitles, I’m just planning to redo bitmap subtitles in DVDs and Blu-Rays that I own to correct mistakes and to give me a bit more control over their appearance.

If WebVTT is only supported as external files, is there any chance that it might also be supported in embedded subtitles in future?