torsion bars / drag racing

Look at it this way. Replace the T bars with say, "2 x 4s" which have NO spring. Now, starting / launching, if the car hooks at all, the reaction of the torque / rear suspension will try to transfer weight and try to lift the front. BUT there is NO HELP from the front because the 2x4's have no spring. Worse, all the unsprung weight of the tires / brakes / suspension will now have to be lifted "dead weight" by the torque reaction. Normally all that dead unsprung weight would "sit there on the ground" and the T bars would push the rest of the car up, transferring weight to the rear.

If there is not enough hook, the whole chassis won't react, and won't generate "hook." It just might sit there and spin.

Now think about T bars. As the car tries to hook, the tension of the T bars helps lift the front, and transfers some / more/ yet more to the rear. You can see this if you've ever jacked up a car under the front spring perches. There's enough distribution that the front also comes up.

Now visualize the relationship of the 2x4s, the heavy stiff T bars, and the slant bars. As others have pointed out, slant bars require more "windup" to support the car. So they push a long ways before they UNwind, and all that push equates to the weight of the lower parts of the suspension and tires staying on the ground

This is opposed to heavy bars, which might be "all unloaded" (practically speaking) before the front tires/ brakes / LCA / other unsprung weight gets off the ground. As soon as all that unsprung weight "has to be lifted" by the rest of the car, that much weight cannot be transferred, so to speak. It is dead weight which the torque of the rear axle is attempting to lift.