So then it seems that Armor Proficiency doesn't determine what armor you can wear alone as with that on 5 and I'm still unable to equip studded leather.When crafting armor it will have a (Normal Armor) next to it. iirc, Studded armor, Rogue armor, Abyssalweave and Chitin armor are all normal armors. Chain mail and Orc are Reinforced while Ebonite and Dultharon are Heavy. Leather and Fairy are the only light armors which require no armor proficiency.
Would be nice to have any information ingame, but I guess I'll have to stick with leather for the time being.