This video is a "how to" but does not demonstrate or prove that inserting the FMC link does anything useful. The speaker refers to "analog noise" but does not demonstrate or prove that such noise, which may exist, has any audible or measureable effect on the output of the DAC.
this is a hobby pursuing well reproduced music... no one is interested in proving anything to you, you are free believe what you want... the video is to inform the op
if anyone really wants to know, they should try it for themselves (as i and others here have)
what you put into the hobby determines what you get out of it