Caitlyn Headshot Scaling [GAMEPLAY]

I was trying some of the new marksman yesterday, and I realized that despite Caitlyn's passive reading "Scales with Crit Chance and Crit Damage" it did not gain any extra scaling from any crit damage runes I had. I felt like this was too obvious a mishap to be on accident, so I figured I may as well submit something on it. All I did was take Crit Damage marks and quintessences and moused over the passive in game only to see it sitting at its standard 50% bonus damage. I'm not sure if it's merely a tooltip bug, of which it could merely not be displaying the added percentage but still calculates it OR if it shouldn't read "Scales with Crit Chance AND Crit Damage", OR if it scales PURELY with Crit Damage from Infinity Edge instead of both Infinity Edge AND runes, wether or not that was on purpose or not I do not know, So I turn to the forums for an answer!

Many thanks!