Braum's Passive (Concussive Blows)

In the C9-IMT game, C9's Braum hit the small krug, and IMT's Cho'Gath then applied stacks with his autos. It seems to me that this is a bug, as the text of Concussive Blows is "Once the first stack has been applied, any allied champion's basic attack on the target generates an additional stack."