But not all optical out is stereo. I don't want to bore you but some HDMI rule states that if passthrough occurs then what is passed when the passing device makes sound shall be stereo. There are some that want to debate but I will not here as it's been done and done.
SO with that out of the way, OTA and APPS which are not coming in on HDMI may emit 5.1 but then it's questionable if 5.1 will be all that glorious in a sound bar. maybe better but for me, well that's my choice.