Yes, Battlefield 1 is a very cpu heavy game. I have an i7 4790 and it runs between 70-100% usage in Bf1 so yes the i7 will indeed be better for this game, but why do you play at medium with a gtx 970? It should handle ultra settings and still get 60fps. Also when you play at ultra the gpu usage will go to 90-100% probably which means removing any bottleneck.
The i5 and 970 should be a fair match together for this game with both parts maxing out.