I trail brake with the rear all the time through bends on both the Rocket and my KTM 1190. It levels the chassis. On the KTM that helps stop pitching when weight transfer from a relatively high centre of gravity and long travel suspension can unload the rear. And on the Rocket it keeps the rear more weighted reducing torque reaction at the back and understeer at the front. Feels nimbler and more sure footed.
In both cases you get smoother, faster cornering and better grip.
Trail braking with the front brake on sports bikes when track riding is a very different thing.