It's exactly why the extra bearing is there, the lateral or twisting force applied to the rear sprocket grinds it to the bushings, damaging them and creating a play. Try to put a load on a bicycle pedals with loosened rear wheel axle nuts -- the wheel will always twist to the one same side. Now add road conditions which considerably increase these lateral forces, and get the idea why i would not want to have a single brake disc when stopping hard or looking for a better control of the braking.
Burgman 650 '04 Exec black (too much a scoot)
Last true 400.
Suzuki DL1000. (gone but still most miles)