IDK about the electronic displays, they should match exactly what the OBD port provides Torque. Sometimes a calibration update is what is required to make this happen. Could be an issue in the instrument cluster also.
On my Edge (mechanical gauge), I have the same issue. It matches Torque precisely till about 60 mph, then it is off by 1 mph, 2+ mph at higher speeds. But it is consistent, I err on the side of caution and rely on the higher reading to be my actual speed for practical purposes.