Tog, the way I would look at is is that while he's inclined his stance is narrow. When he stands up through neutral his stance is wide. That particularly segment he is choosing to keep this ski track width fairly constant.
There is a time and place for both wide and narrow stances, I'm not meaning to endorse or demonize either one. Was just answering your question about why someone may have called Lorenz's inclinated stance as narrow. Many people view that as narrow stance with vertical seperation. Its also possible for your leg stance to remain constant while the skis get wider and narrower through the turn, or conversely its possible to keep the skis fairly constant width while the stance between the legs changes as in this video.
With really big edge angles and/or on steeper terrain, vertical seperation can become more pronounced with the inside leg shortening a lot, the knee coming up quite high and the skis will simply be wider on the snow at the apex then what might be ideal at transition, therefore some amount of diverging and converging skis is not uncommon and not neccessarily wrong. But its not either neccessarily wrong if your tracks are parallel, as long as your stance is functional. Functional stance is way more important then whether your tracks are parallel.
what is a functional stance? Depends on what you're trying to do. There is no one size fits all. There are many over-simplified views on stance floating around. Wider stance is more stable if you're close to 50/50 balanced on them. But what if you're not? On the other hand, how often do we actually need to be in that kind of stable golf cart state of balance? We are constantly moving back and forth across the skis. Narrower stance makes it easier to get your CoM moved across the skis. On the other hand, slightly wider stance creates a wider zone of neutral, in other words it takes longer to move through neutral. is that good or bad? depends a lot on what you're trying to do. Moving onto the LTE of the inside ski is a lot easier in some ways with a narrower stance, you don't have to move your knee as far inside. On the other hand, a little wider seems to inspire a bit of foot independence. If your skis are really wide, it will be easy to find yourself on the opposing inner edges. Narrower stances will freak out your ski school boss. If you are racing a wide stance can create instability when you release the downhill leg by relaxing it and create a stronger toppling movement through instability. That can create a super fast turn entry, if that's what you want. If that is not what you want, then maybe you have to handle it another way. There are so many different situations and there is not a single one size fits all optimal ski track width or stance.
Skiers should not be trying to remain in a fixed wide stance, or fixed narrow stance, they should just be skiing functionally. Functionally can include a foot separation that changes throughout turns or not and can be narrow or wide, depending on what you're trying to do.