I think calling something "Mithril Studded Leather" is like saying you drive a "Plastic Car" because the stereo buttons are plastic. Studded leather is simply that. Studded. Not Plated leather, or any other way to describe it.
The amount of metal is negligible at best.
Leather Armor = 20 lbs
Studded Leather = 25 lbs
Official description:
Studded Leather: Similar to leather armor, this suit is reinforced with small metal studs.