I never seen the White Crane Sai form done with a tornado kick. If the video was a demo, then perhaps the performer, I haven't seen the video and considering the performer does Long Fist as well, may have just added the tornado kick for performance purposes.
Tornado kicks don't exist in our White Crane style. Southern styles don't originally practice jumping spin kicks. Our Crane do have a jump kick but it's more frontal like a jumping toe kick. No spins. Although Southern styles emphasize low kicks, there is the occassional jump or high kick but it's more seldomly done. Just like Northern styles are more emphasize longer range and longer, higher kicks, they still have their short range techniques. Longfist has elbow strikes and trapping and sticking as well and can easily low kick or short low kick. You wouldn't question, why is Long Fist doing elbow strikes or low short kicks? Even Long Fist gets into short range. Short range techniques are there in Long Fist/northern styles. And vice versa for our southern Crane, that although it's mostly short range, there is still the occassional jump front kick.
As for Master Yang in that Fu Hu Bu like stance in the black&white pic of him doing White Crane, look at his leg that's extended. The knee is still bent. White Crane never straightens out it's knee.
Not all the definitions or generalizations of southern or northern or external or internal is really that black & white. Sometimes the execution of the patterns or techniques are outside the box when you try to match it to the generalized definitions of what makes it that specific style.
Like Hsing Yi. It's categorized as internal. But the way they strike or be explosive is different from Tai Chi being explosive with fa jin. Internal is categorized as being soft right? I don't practice Hsing Yi, but it doesn't seem to contain that same softness as Tai Chi even when Tai Chi is explosively striking. Hsing Yi seems almost White Crane like. With the soft hard emphasis. Where Tai Chi is more softer. Perhaps what makes Hsing Yi internal is to still try to use internal power to execute the movements. But the body mechanics don't seem so soft. So how can we say that internal completely means soft?
Our southern Crane can stick and follow. But sticking and following requires softness. Well if you softness, how can you call our White Crane external now? External mean hard right? Or at least that's how it's been defined in English when trying to explain Chinese Martial Arts.
Don't take everything too literally. It's difficult to translate Chinese to English. Something gets lost along the way. Sometimes you have to think outside the box when it comes to English translations of how Chinese Martial Arts is explained. Cause likely you're not getting the whole story. Rather than looking at a style and immediately categorizing it, "oh yeah, that's an External Southern style", why they're doing that.
Maybe cause Master Yang was a kid in that pic and his stance was off. Or maybe he's doing it right cause his White Crane master told him to have it extended that far? Maybe he's in the middle of moving and he naturally fell into stance that way?
What constitutes as a low stance? Thighs parallel from the ground? How come in the Crane ma bu with the knees turned in you can't get the thigh to turn parallel to the ground? Does that mean sinking as low as you can in the Crane ma bu isn't low cause your thigh isn't parallel with the ground? But a Long Fist fu hu bu, which has thigh parallel with the ground, is a low stance?
The masters talk about get low, sink into low stance in training.
But when you see these old black and white pics of some masters they're standing medium hieght and their thighs are not parallel to the ground. What does it really mean to be in low stance then? Is low stance a physical thing or an internal thing to really sink your root down?
A beginner with their first few years should emphasize a physical low stance to physically and externally lower their root. Cause a beginner can't root down internally. As the practitioner develops stronger legs and has the sense of being low physically by literally standing low, internally they should push their rooting lower. So that as years go by, as they stand higher, the root should be getting deeper. To the point where when they stand straight up, they're very rooted but internally.
Ponder upon what the masters say. Answers are often not so black and white. Look at things below the surface of all the talk and see what they're really trying to tell you. Because there are somethings that words cannot explain. Lots and lots of practice and pondering for several years. I used to think that after 9 years I'm just scratching the surface. But lately I've come to realize, I haven't even begun to scratch the surface. I'm still learning new things and discoveries. I though I knew Lien Bu Chuan. But I really don't and I'm researching through practicing it now.
Enough of my rambling. I hope that all made sense. Cause really, I may not know what I'm talking about. In ten years I'll probably laugh at this and see I'm not that advanced. May 20 years later I might begin to understand my Long Fist basics. So I hope I answered the question. If I didn't, I'm sorry. I don't know much.
I think this post may sound like I'm yelling at you. But really I'm not. I'm just rambling on.
This is a thought world part of a thought universe. Man is the center of thought. "I think. Therefore I am."