Ligety mentions the same leg extension/push at the top of the turn a little later in the article, which I thought was interesting.
I'm kind of curious, just being the baby of this place – was there a culture of skiing pre-2000s where the inside ski was used more? I've heard a couple of skiers from that 2000s era who really emphasize the outside ski, and I can never tell if it's a reaction to actual novice questions, or if people were teaching the inside ski usage earlier on & the discourse pendulum has swung back and forth a bit.
Outside ski dominance has been taught and emphasized since at least the mid-1960s, when I took my first lessons at Badger Pass under Nic Fiore. It was definitely part of PSIA dogma in the "American Teaching Method" in use when I started teaching, and has carried over largely unchanged to ATS (the latter needed a name change to "system" from "method," because of course it did).
Crucially, foot-to-foot pressure control must have been practiced long before that. In the mid-1800s when Sondre Nordheim was demonstrating and popularizing the Telemark and later Christiana turns, he and other skiers of the day had to have felt and known the difference between the relatively even weighting and outside-ski lead that characterizes Telemark and the lighter, inside-ski lead in christie turns. (But no, I wasn't around then.)
In any event, since at least the 60s there have been tons of drills, progressions and written materials focusing on how and why to pressure the outside ski, big toe side, etc.
Lastly, it's telling that while Ligety and seemingly everyone continues to emphasize outside ski dominance, videos of top racers including TL often show surprisingly heavy inside-ski weighting, with telltale snow spray. I see these skiers edging before pressure with an obviously keen ability to ski on any of four edges at will. While weight naturally belongs on the outside of most turns, timing is key. Furthermore, in my own skiing and teaching a lack of comfort and finesse on the "weak side"—meaning the outside edges of our feet and skis—is the much bigger problem, especially among high-level skiers.