Actually, higher sensitivity is more sensitive - it corresponds to how much the accelerator is pressed down, so you will be at only 99% thrust if the button is 99% down, which is stupid because nobody wants to actively force their thumb down all the time like that.

Low sensitivity divides the sensitivity into brackets, i.e. holding the button down 13%, 3%, etc. will equal 20% thrust, so there's about 19% extra leeway if you're not holding the button down all the way down, so you'll still get 100% thrust. (I'm just guessing at the brackets, they're probably more likely to be divided in 10ths than 5ths, maybe more)

High sensitivity doesn't mean you only have to hold the button down a little bit to get full thrust.

It's only counter-intuitive at face value, but when you think about it, sensitivity can be looked at in more than one way.