That is not true at all. A manual trans race car can be very consistent. Ever watch Pro Stock?
Automatics have many advantages then just being consistent. They don't "hit" the tires as hard, usually have less steeper gearing than a manual, have torque multiplication with the converter and so on. Plus to get a high HP car to live and work best you have to periodically need resurfacing flywheel and clutch disc surfaces, rebuild the pressure plate, changing finger weights and so on. Racing a high HP car with a clutch takes a lot more maintnance than most even realize. There is a reason higher horse power race(d) cars use automatics. Consistency is only one part of it.
All things that can be changed out or modified, ive done it all. My SC Drag car has an auto because its consistent. Thats about 90% of it, but im seeing 6 sec passes. And Usually those High horspower cars have a hybrid tranny, its not just AUTO. like F1 cars, WRC, ALMS GT, use automated clutches, some* cars have up shifts controlled, but almost all have down shifting driver controlled, driver still rev matches. There are PLENTY of manual options out there with a different egagement mechanism. The other thing that these Auto guys dont understand from thier coolio ford auto tranny to an actual racing tranny thats actually pulling the high HP and crazy times is the "dogs." Dogs are basically no more than cogs on a slider. The shifter pushes them into a receiver ring which engages the gear it is attached to. There is a separate dog and receiver for each gear in the transmission. On a racing transmission, there is a lot of "slop" (the gaps in the receiver are a lot larger than the teeth on the dog), which makes it easier to move into and out of the gears at higher rpms without fully engaging the clutch. Just like a full-blown race car, a racing transmission would be a nightmare around town but is a dream come true on the track. So in essence just becasue you bought a ford 5.0 Auto car, you are not on your way to High HP builds and single digit timslips just all free willy...