Actually, on several cars that I've seen, its the opposite: If the front and rear wheel speeds don't match, it may retard upper end power.
It may have absolutely no effect at all.
I can see how it could be rumored, more than likely, its a twist on the true statement that faster 1/4 mile times can usually be achieved with the traction control turned off.
On a brake based traction control system, the brakes are modulated by the ABS valves to slow the wheelspin. There would either be a single speed sensor reading a large tone ring next to the ring gear if its a 3 channel system, or else an individual wheel speed sensor reading a tone ring at each axle/brake/hub, if its a 4 channel system.
I know when I was working on these, we did also send messages to the engine control for torque reduction.