The only thing it's doing is doubling the wear on the throw out bearing and clutch linkages. I've seen taxis with 300k miles on their 3rd clutch but never having any gearbox components changed.
Not that wikipedia is the end-all, be-all authority on double-clutching.
"While double clutching is not necessary in a vehicle that has a synchronized manual transmission, the technique can be advantageous for smoothly upshifting in order to accelerate and, when done correctly, it prevents wear on the synchronizers which normally equalize transmission input and output speeds to allow downshifting."
"While double clutching is not necessary in a vehicle that has a synchronized manual transmission, the technique can be advantageous for smoothly upshifting in order to accelerate and, when done correctly, it prevents wear on the synchronizers which normally equalize transmission input and output speeds to allow downshifting."
https://en.wikipedia.org/wiki/Double_clutching_(technique)