Not tried it ummmm but it is supposed to give a richness by adding a slightly beaten egg(all) also I used to add cold milk but warm does make them fluffier.
I always used to peel my potatoes even new ones if making mash, but we went out for a meal and the potatoes were gorgeous mashed with the skins on now it's the only way I do them.
He warmed the peeled spuds through in a pan of water at 72F for about 30 mins to lock in all the starch. Then in fresh water boiled them for 20/30 mins. drained them and put them through a potato ricer and then rubbed them through a sieve and then added 25% of their weight in butter and beat them and added some potato flavoured milk made by infusing hot milk with the peelings from the potatoes. I think that is how he did it ummmm. His three times cooked chips looked good but to be honest homemade oven chips can be just as good