Match grading system issues for supportive junglers

I play a lot of Sejuani... a LOT... but there seems to be no factors in the grading system that grade well for a jungler with a support playstyle. Tank junglers are a lot like tank supports in that they don't farm super well, they don't deal a ton of damage, and they don't get a whole lot of kills. Tank junglers gank often and provide CC and engage much like a support Leona would, making it easier for the laner to get a kill. However, a match that would get me an S on Leona support (as far as contribution goes) only gets me a B on Sejuani jungle.