Unsure, possible AD exploit

I was in a game earlier today and was truly stumped at what was going on. I did some research after the game just to make sure, and I can not for the life of me find out how this Jarvan had so much AD. Here was the situation: I found out he was using a page of nearly full scaling AD runes. At level 8-9 he had around 60 bonus AD from sources OTHER than his items. Based on his runes, and the scaling AD mastery, he had: .13 per level from red runes, nine of them. .04 per level from blue runes, five of them. .06 per level from yellow runes, nine of them. .25 per level from quints, three of them. .55 per level from his mastery.

There are NO other ways to gain bonus AD from masteries that I could see, so I did the math at level 8. 9.36 AD from reds. 1.6 AD from blues. 4.32 AD from yellows. 6 AD from quints. 4.4 AD from mastery.

For a grand total of 25.68 AD. He had over TWICE this amount from sources that were NOT his items. He had a completed Ymou's and a Phage at this point in the game, which is 80 AD bonus. He had a bonus AD value at level 8 of 135.

So not sure if there is a bug of some sort with scaling runes or not, I don't have them to test. It's possible this was exploiting a bug, but he had so much bonus AD from sources that were not his items, runes, or masteries that he was practically 100-0 everyone in the game because of Jarvan's high scaling ratios. Just wanted to bring this to someone's attention.