Position an oven rack in the top third of the oven and preheat to 425 degrees F. Prepare the wild rice as per package instructions (discarding any included flavor packets). Keep warm and set aside.
Meanwhile, toss the cabbage, garlic, 1 tablespoon of the oil, 1 tablespoon of the vinegar, 1/4 teaspoon salt and a few grinds of pepper together on a baking sheet. Spread out leaving room for the pork tenderloin in the center.
Sprinkle the pork with 3/4 teaspoon of the apple pie spice, 1/2 teaspoon salt and a few grinds of pepper. Heat the remaining 1 1/2 teaspoons oil in a large nonstick skillet. Add the pork and cook, turning as needed, until brown on all sides, about 5 minutes. Place on the baking sheet and brush the top and sides of the pork with 2 teaspoons of the mustard. Roast until the cabbage is tender and the internal temperature of the pork registers 145 degrees F on an instant-read thermometer, 25 to 30 minutes. Transfer the pork to a cutting board to rest for a few minutes and then slice. Toss the parsley with the cabbage.
Toss the apples with the remaining 1/4 teaspoon apple pie spice. For the sauce, stir together the sour cream and the remaining 2 teaspoons mustard and 1 teaspoon vinegar. Divide the rice, cabbage, pork and apples evenly among four dinner plates. Spoon the sauce over the pork. Serve each with a glass of milk.