While I am a big believer in good power cords; I am very skeptical that there is really a specific power cord for digital components.
Let's say I make power cords. All of the cords I make are identical in every single way, except for the color of the outer jacket.
I decide the cords with the red colored jacket are for digital. I can now say on the package that the red cord is made specifically for digital, even though they are really all the same.
A manufacturer can save money by making some unshielded cords, then charge a premium for the shielded ones.
Not all applications need shielded power cords. Using a shielded cord when the shielding is not needed has no effect. So you could just buy shielded cords or cords designed to eliminate RFI and forget the rest. There are ways to eliminate RFI in the power cord without shielding.
Just try some cords and buy what sounds good to you. If you can't tell any difference like Dr. D then you've saved a bunch of money.
Good power cords are definitely NOT snake oil. But snake oil marketing is used by some companies to sell their products for more than they are worth.