A little harsh tbh, it did used to be for technical reasons which I don’t believe exist in the lower end newer devices anymore but don’t quote me on that. If you are using older devices (chrome bummer for example) you need to follow the advice still as it can lead to osolation, over heating and then a pop. Whether true or not it will void OPs warranty using something different than what stated.
But if that doesn’t bother you, it doesn’t need to be there cable it just needs to be to there spec. It just they guarantee it.
Anyhow OP, the dirty secret is to use linn k20 it’s built to naim’s “spec” big circus about it back in the day that lead to naim redesigning and creating the naca5. Linn k20 is the older naca4.
The k20 is (well was don’t know if it still is) nice and cheap a well machined.