Aliminium Shuffler that is complete nonsense. Practice is enormously helpful, that's like the people in football who say it's pointless practicing penalties because you can't recreate the pressure of a real match scenario. Fact is if you practice enough that it becomes a motor skill then the effect of pressure becomes drastically less.
Many people I know passed the BA crosshairs and number sequence test after practice because it soaks up so much capacity if you're having to think about your every movement of the joystick with FD's moving in the reverse sense. Once you make that become a motor skill your brain is totally freed up to concentrate on the number sequence.
Can't/shouldn't practice? Absolute nonsense, folks.