As you note in your original post, "paradox" is just another term in the hobby that holds zero legitimate value other than as a descriptor.
I have always used it to describe an animal displaying areas of pigmentation/pattern that are contrary to the accepted base morph of the animal. So, in terms of pigmentation, an Albino animal with a patch of normal melanin pigmented skin would be "paradox" and, flipping it around, a normal coloured animal with an Albino-like amelanistic patch would also be "paradox". A pattern-type "paradox" would be a Spider with a patch of WT patterning on it or, flip side, a WT with a patch of Spider pattern
As far as using "paradox" to describe a ringer... Nope. Without going too deep in the weeds, how ringers occur is not a total enigma -- it is most probably a single mechanism at play