Well you know what they say……” you can take a horse to water………..”What I get from that is, so long as the source sending the signal and whatever is receiving the signal are working fine and were properly designed, there is no affect on SQ. Problems may be encountered due to jitter and various forms of interference. At 8.17 in the video, various problems that can affect the signal are mentioned and suggestions as to how that can affect SQ, but no examples are given. By that I mean, if the jitter is measured at such and such, then that means "reduced deep lows" or a "loss in resolution".
Why does he not show a specific cable against another cable and play or measure the difference? I want to hear the "reduced deep lows".
It seems to me that something has to be seriously wrong with the design or equipment for there to be an audible effect, and no maker is going to sell a product that just does not work. The video also states the likely problems will be with the digital/analogue conversion and is not specifically about cables causing those problems.
An Amazon basics optical cable at £4.99 is going to be well enough made that it is not going to have an audible effect on SQ, compared to another at £70.