You're right there.
Here's a scenario- You could have an mildly modded old low tech, big cube, push-rod 2 valve V8 that made the same torque at 4500rpm as a worked RB whatever, but what happens to the V8 the harder you rev it? In most cases, the torque curve drops off like you just pushed it over a cliff, and therefore the car is no faster when revved. The 'Line on the other hand has just started to come on boost hard, and holds or increases that torque value for 1000's of rpm more- thereby having a much higher power and torque level in the upper rev range than the V8. And thereby giving better acceleration when launched correctly.