Actually, the difference is 3 mm in spacing, standard SD buckers (and almost all vintage Buckers) have a 49mm spacing.
I´m not gonna say anything about SK because there´s not much to say either way. But If Lew can hear it, quite a few of my buddies can hear it, the magnetographs at work plotted one, I´ve recorded one and demoed it it back to myself, and most importantly my ears can hear a difference (I was highly skeptical too 10 years ago, long before I even had internet): Then I´m inclined to believe there is one.
If some people can hear the difference between a Dimebucker with and without brass inserts in the legs (sounds like total crap with them, I sold it afterwards as surface mountable after drilling them back out), then I´m more than inclined to believe that a difference in string alignment will be audible.
THis is not intended as a bash on anybody, but bottom line: just becasue your senses don´t sense something doesn´t mean it´s not there... it often only means you can´t see /hear /taste /smell feel it...
For ex. I can´t taste, smell or even see a difference between a Kebab at Sofra and a Kebab at Sultans... but others swear by the difference that Sultan´s meat is spicier and less dry. Yet I don´t assume that nobody else can taste it either, because I´m not an Übermensch