Nov 10, 2020, 18:3311/10/20
I just confirmed that this works on not only Perception sets, but also Crit Damage and Fatal sets as well. These are the sets that I had on my Fylja before applying "Lore of Steel". So it should be able to affect any stats in the screenshots below. Below are before and after pics.
Before adding "Lore of Steel" mastery:
After adding "Lore of Steel" mastery: