One of the ideas is that different stats should have different weights in the skill. I.e. dex and rea is more important for attack than int.
I won't be coding this, though I see its merit and would prefer it as a system. That would open the door to all manner of balance related issues, in fact adding a very thick layer. As a proxy to this, we have the ability to give stats more weight by counting them multiple times in a skill's keys. For instance, if dexterity should be the driving force behind attack, it would appear as:
Stat: dexterity, dexterity, strength, reactions, intelligence, endurance