I don't think all skills are based on the appropriate stat, which may be a heritatge from the days when Darke had fewer stats than it currently does. Some examples:

Stalk: Uses dexterity. Reactions?
Being quick and reacting fast enough to what your target is doing to follow it as I see it.

Skin corpse: Uses strength. Dexterity?
Hum... Sounds obvious to me. using a knife to skin a corpse is more fine work than brute strength to me.

Consider lock: Uses dexterity. Intelligence?
You are considering the lock, examining it, trying to determine it's type, NOT doing the dexterity-intensive picking.

Reverse stroke: Uses dexterity. Reactions?
Well, reacting quick enough to reverse a backstab seems like it should be reactions-based to me.