Originally Posted by kitchen_space
I was watching this bluray that came with my oppo, and the guy on it stated that toslink and digital coax use S/PDIF, which is only capable of 2.0
You misunderstood Dr. Waldrep. While the S/PDIF protocol is limited to two channels of PCM, it is more than capable of sending encoded multichannel audio such as DD 5.1 and DTS Surround. Those are the formats that have been used on DVD for years. Many TV shows also have DD 5.1 soundtracks.
Optical and coax can send stereo PCM and multichannel DD 5.1 and DTS.
HDMI is needed for multichannel PCM and lossless codecs such as TrueHD and dts-HD Master Audio.
So, returning to your original question, when a station says "Broadcast in 5.1", that means it is using DD 5.1, a format that can sent over an optical or coax connection to a receiver for decoding.