That's what Rivals has reported, doesn't mean it's true/accurate. Notice how it doesn't have a check mark next to it, means it wasn't authenticated. I've read somewhere he runs around a 4.7, which is plenty fast. The 40 yard dash for D linemen is a dumb measurement of quickness. 10 yard dash/split is what it's all about. Measuring the quick burst of the line.
One of the biggest misconceptions that emerge from the NFL scouting combine each year is the importance of 40-yard dash times. The 40 is the considered the glamour event of the combine, and every year NFL executives, scouts, draftniks and fans get carried away by some of the mind-boggling times. This often puts too much value on a player’s ability to run fast more than it does his pure football talent. Am I saying that the testing at the combine isn’t important? No, but the test needs to be evaluated more from a football-related standpoint. One of the most important and consistently overlooked measurements at the combine is the first 10 yards of the 40, known as the 10-yard split. This is simply a measurement to see how fast a prospect can cover 10 yards. It’s great to see how fast someone can run 40 yards, but how often in an NFL game are players required to cover that distance on one play? A more reasonable measurement, and a better indicator of “football speed,” is 10 yards.