Interesting result. I think I may have subconsciously primed myself for a better performance as the prompt told me that it was about to go back to "normal".
I suspect I'd be a lot worse if it switched me without warning.
The reaction difference would theoretically be amplified over time, and if you were to take the test for 30+ minutes a few times a week, the impact would (again, theoretically) be greater.
OTOH, I was consciously visualizing the mirrored position of the target circle on screen and navigating toward that without looking at the mouse cursor, so mentally it's exactly the same movement as the pre-rewire step.