the caution is confined to the audiobooks and seeks to provide context, stating, “The first book in the Discworld series – The Colour of Magic – was published in 1983. Some elements of the Discworld universe may reflect this.”
That’s it. That’s the whole “story”.
Penguin Random House delineated that the notice should not be misconstrued as a trigger warning, but rather a note meant to situate the reader in the timeframe of the book’s origins.
There is absolutely nothing wrong with this. That whole site smells.