By the time of those George Lucas quotes, he’d already filmed the movie and decided against having any nudity. But the concept art was done at a time when the script was still in flux. Going “the Disney route” wasn’t necessarily a decided thing in 1974-5.

Besides which, costume designer John Mollo wrote in his notes from 1975 that Leia’s outfit was to be “mock-medieval” but also “Tarzan-type” (apparently for the prison escape). Which fits with the loincloth in the McQuarrie sketches.

And as I said above, there was basically a rape scene in the 1974 rough draft with a “half-naked” Leia and the “Urellian trappers”, which was indecent enough that JW Rinzler shied away from describing it on the official SW site.

I really think it’s your own assumption that, since SW is “family-friendly” now, it must have always been that way from the very beginning. The evidence suggests otherwise.