The quotation you refer to doesn't nullify Sacha's point. It says it's a "catch-all term for when objects retain ornamental elements of the past." Sacha says the blue leather texture example is NOT skeumorphic because the textures did not exist in past iterations of the product, since there was no original to begin with.

If I translate a physical object into a digital version and replicate ornaments that add no function in the digital version (ie. a leather texture), that's considered skeumorphic. On the other hand, if I apply a leather texture to my UI for random app X, that's not skeumorphic.