All right, I'll bite. It's a good question, and an important one for understanding ski technique, troll or not.
[EDIT: For those who are already lost, a couple simple definitions: A "Wedge Turn" is a turn made with the skis converging--tips closer than tails--and with both skis gliding on their inside edges all the way through the turn. A "Christie" (or "Christy") is a turn or any part of a turn with the skis on "corresponding edges"--both right edges or both left edges. Usually, in a "christie," skis also tend to be roughly parallel. So a "wedge christie" is a turn that starts with a wedge, and finishes with a more parallel "christie phase."]
As others have very well said, the progression from wedge turn to wedge christie to parallel turn is the natural outcome of developing skill, increasing confidence, and perhaps going a little faster, with the EXACT SAME fundamental movements. Or at least, it WOULD be if the movements were taught correctly from the beginning (they often aren't).
The important movement of any ski turn is, of course, that the skis TURN--like the front wheels of a car. Whether this happens due to skis carving or the skier actively steering them, or a combination, is not important. It must happen either way, and if it doesn't, the skier won't turn!
For a turn to actually cause the skier to go in a new direction--as opposed to just one that slows him down--the front ends of the skis must turn IN to the turn, rather than the tails twisting out (into a skid). For this to happen, the inside tip (right tip of a right turn) must start turning first--otherwise it is in the way of the outside ski.
So a very simple thought for initiating a good turn, whether in a wedge or parallel stance, is "right tip right to go right, left tip left to go left." And everything else will follow from here. With low skills and low speeds, most beginning skiers will show a bit of a wedge as they turn both tips down the hill to initiate a turn, even if they start from a parallel stance in a traverse. Why? The downhill ski is simply harder to turn at first, because it is difficult to completely flatten it on the snow, and because it typically supports a little more weight. (Flattening it completely to initiate a parallel turn becomes much easier if you have enough speed and confidence to tip your whole body downhill/into the new turn--not the case at very low "beginner" speeds.)
So "right tip right to go right" typically causes a gentle wedge, even as BOTH tips are guided down the hill. Then speed picks up as the skier glides downhill. The skier tilts into the turn for balance, helping flatten that inside ski, and weight moves progressively toward the outside ski, lightening the inside ski. At some point it becomes easier to turn the INSIDE ski, so the same "right tip right" effort brings the skis parallel as the skier continues to steer both skis through the turn. Voila--a wedge christie!
Soon, with a little more speed, and a little more skill and confidence, the skier will be able to completely release the downhill ski at the start of the turn. The wedge christie becomes a parallel turn. But the movements and the skier's intent and efforts all along remain exactly the same. We do not teach wedge turns, then wedge christies, then parallel--we teach fundamental movements and help skiers develop skills. The wedge--wedge christie--parallel progression simply identifies typical "milestones" that skiers pass by/through as they become more proficient.
I agree with Wigs that the progressions and exercises that lead to these movement patterns are the same in both "wedge" and (good) "direct parallel" progressions. As I have often said, the wedge/parallelness of the skis is irrelevant to these movements!
But a "wedge progression" that teaches skiers to push out on the outside ski, or to make what I call "negative movements" of the body to the outside of the turn does NOT develop these movements. It could properly be termed a "dead-end progression."
Likewise, a "direct-parallel" progression that teaches negative movements is also a dead-end progression. The little spontaneous wedge at the beginning of the wedge christie could be avoided by shifting the weight completely to the uphill ski first, but this shift involves a movement of the body uphill in order to balance on that uphill ski--a negative movement, a dead end.
Here's a graphic from my book that illustrates very simply the correct movements for a wedge christie ("matching") and the incorrect, "tails out" (negative) movements of "closing."
Of course, the "tails out" movements, while inappropriate for an offensive TURN, are quite appropriate for defensive intent or braking. They are the movements of the classic "Stem Christie." If you want to "go that way," you need the TURNING movements. If you just want to "stop going this way," the defensive movements are just right!
Those who find fault, categorically, with the wedge in a beginner's progression, or who assume that any "direct parallel" progression is "good," simply don't understand these important concepts.