To me the whole cable directionality thing seems to be rooted in the complete misunderstanding that a signal, as a discrete thing, passes from source to speakers having been boosted and amplified at each stage. When this was pointed out then all the spurious stuff about diode effects and such was made up to counter it. Then when it was pointed out that the signal was AC and how that worked some other non-applicable science was spouted.
For me it's up there with Flat Earth and Big Foot.