Hi Martin,
Well, in this case, the result is the same, because you are saying the first driver is using y=2-x, which for x between 0 and 1 goes from 2 to 1, but you have set the property to be clamped between 0 and 1, so that always results in 1. the same would be if you set the coefficient to something higher than 2.
I hope that makes sense.