Found out it wasn't a part of the game at all but my resource pack, there is no bug.

I'll try to double-check my resource pack first before going here.

Short grass, leaves, and the top of grass blocks seem to blend extremely well to the savanna theme, but tallgrass specifically won't, I don't know if this is a bug, or an intended feature. 

As you can see in the image the tallgrass (2 block high grass) stands out from the smaller grass (1 block high), The Leaves, and the grass. I don't think this is intended but just never considered. even then I don't think I should have to make all the grass specially made for each biome just to compensate 2 block tall grass.