NBC app on Apple TV only outputs stereo audio

I am only getting stereo audio output from the NBC app on my older Apple TV. Is this a limitation of the NBC app? I do get Dolby Digitial from the Netflix app on my Apple TV. I tried searching the internet, but didn't find any information regarding the NBC app and it being limited to stereo audio output. I am running the video and audio through an HDMI into my receiver, and then into the TV. Again, Netflix plays in Dolby Digital just fine..