jjss49 posted the video in response to "And how is FMC better than ethernet cable?" It did not deal with the question of how FMC is better than ethernet cable; it merely showed how to do it.
As for the popularity of the Sonore Optical Rendu, it is an Ethernet-to-USB convertor and not just an inserted optical link.
And, yes, the question would better have been answered by user comments.