If you are anchoring different with the BT release, then you may have to adjust your sights. If you're putting torque on the bow (or eliminating torque with your new technique), and causing the arrowing to fly different, then you either have to always torque it the same or move your sights.

When I use a back tension release, my sight must be adjusted. Not 6", but a couple inches at 20 yards. For me, it's because I anchor slightly different and my BT release is not as close to my face as my trigger release. The reason is because the back of my hand is against my face when using the BT release and it is not with my trigger release.