Yes, the 20-minute cook time is correct for this recipe. By baking at a high temperature and keeping the oven door closed 2 hours, this roast cooks up extra tender and flavorful. Don't open the oven door at any time during the 2 hours, or you will lose heat; then the roast will not get to the proper temperature. If the meat has not reached 145° when you check it, put it back in the oven and bake at 325° until it reaches at least 145°.
Combine cream cheese, horseradish, and mustard; stir until smooth. Cover and chill.
Combine wine and butter in a large heavy-duty zip-top plastic bag; add roast. Seal and chill at least 8 hours or up to 24 hours, turning occasionally.
Preheat oven to 500°.
Remove roast from marinade, discarding marinade. Place roast in a 13 x 9-inch pan lined with heavy-duty foil. Combine salt and pepper, and rub over surface of roast.
Bake, uncovered, at 500° for 20 to 30 minutes. Turn oven off. Do not open oven door for 2 hours. Meat thermometer should register 145° (medium-rare) to 160° (medium). Thinly slice meat, reserving pan juices. Serve meat with pan juices and horseradish cream.