DTS via airplay downmixed to stereo?

I was trying my first DTS movie just now, but it seems to downmix to stereo over airplay. I don’t know if this has to do with the airplay spec? Has anyone else got it playing DTS over airplay?

DTS over AirPlay isn’t supported yet, as the Apple TV doesn’t support DTS audio.

We’re looking into a few ways that may help work around this, but don’t yet have a definite answer on if or when this may be available.