While I may never get around to trying it, it seems obvious to me that this test takes advantage of effective speed you can gain in pro mode which you can't attain in lesser modes.
It's easy to wheelie lots of bikes in the easiest mode, right? But impossible or almost impossible in harder modes? That seems somewhat counter-intuitive (i.e. you might think fore-aft sensitivity would increase, not decrease, in harder modes), but suggests perhaps you can actually accelerate harder in some cases in the "harder" modes without losing front-wheel traction.