These are 2 quotes I found doing a quick google search looking at torque reserve, shifting and the 392.
Other writings seem to indicate that maybe shifts may be quicker and harder and that engine power is not reduced as much (if at all) during the shift. Hopefully it is true balls to the wall, but I'm gonna have to get out there and do more research.
Torque Reserve is a type of launch control for on-pavement antics allowing the Rubicon 392 to eagerly grip solid-pavement, accessible during a brake torque launch. AMax shifting makes the most of engine torque and cog swaps, the same found on the Hellcat-powered Grand Cherokee Trackhawk.
The Wrangler Rubicon 392’s powertrain calibration includes Torque Reserve and AMax shifting, accessible when doing a brake torque launch, that delivers maximum acceleration for solid-pavement launches. Torque Reserve, an engine strategy used by drag racers, manages fuel flow to the cylinders and controls spark advance or retard to balance engine rpm and torque to maximize power delivery and launch performance. AMax shifting, a performance-enhancing strategy used on the Jeep Grand Cherokee Trackhawk, maximizes forward torque by coordinating shift time and engine torque management.