In extract brewing, the specialty grains are steeped, not mashed. Most of the time, specialty grains are not enzymatically active. Steeping extracts color and flavor, but little to none of the starch becomes sugar.
In mashing, you're still steeping, but with enzymatically active malt, like pale 2-row malt. In your case, the Red-X is active. This brings out more from all of the malts, increasing your gravity and the color/flavor punch of specialty grains.