As @Heavens AAA explained, we need to count points in order to prevent ties, too, the effort should exist and have a value. We don't have so many displayed information in the stats to use other values, easy to track for all, for these challanges we do.
Manipulation is a handicap too, so by forcing people to earn MotM -which can be earned by doing a sub of the most rated players in a live match, in case the GK is between the 4 best-, and counting the goals assists, we have more chances to tackle a bit the effect of manipulations.
We've been doing this for many months, there's a reason why we have some criterias for the forum challanges we do each season and too for the AvQ limits we use in the tournaments I run since 2013.