My 2018 SRW, once warmed up will downshift about the same as yours on a steep incline. 5mph drop and it downshifts with the typical shift flare of unlocking the converter. Going down hill it does not down shift unless I the cruise control is ON. Exhaust brake is always ON, but not AUTO. Tow/Haul mode is always ON. My speed is always around 65MPH on cruise. The torque converter lock up is disabled until my engine/trans has warmed up.