It's funny how obscure S/PDIF is despite being (1) the only consumer fiber optic connector, (2) being on a whole lot of gear (almost every DVD player) and (3) being a real answer to the noisy electrical environment inside a PC and the effect that has on sound quality.

It's also obscure that you can make a CD with data in the right format,

https://www.discogs.com/search/?q=DTS-CD&type=all

and connect a CD player with a S/PDIF connector to almost any home theater and you have multichannel music. I have a big Sony 300 disc CD changer that is half full of 5.1 discs and I like how I can put together very ordinary hardware to get extraordinary sound.

I don't understand how using fiber connector for audio fixes coil whine, as coil whine is audible noise generated by the GPU, not noise generated on the analog audio transport. In this case I think the problem would be EMI generated by the GPU, not coil whine- unless audible coil whine is associated with EMI.