Conventional automatic gearboxes rely on the slippage in the torque convertor to avoid the stall/shudder effect.
Most autos now come with a lockup torque convertor that electrically or hydraulic locks the turbine and the stator together, hence they avoid the slippage and increase efficiency and mileage per gallon. The cars ECM tends to command the convertor to lock up based on speed, which gear it is in, load on the engine. When you brake, they convertor unlocks. You can tell if the convertor is locked or not by driving, say at 50mph and flicking the brake pedal with your left foot. The convertor will unlock, revs will blip upwards and then the convertor will lock back up again, and revs will drop.
When I used to drag race an automatic, 1987 Buick with a four speed auto trans and lockup convertor, you could (knowing where to break in to the circuit) install a switch that forced the convertor to lock. This tended to give you a bit more mph on the run (no slippage). You had to remember to flick the lockup off though as, when you slowed down to manouvre, the torque convertor acted like a conventional clutch and the car shuddered like a manual in the wrong gear.
Manual trans cars are frankly, and literally, a waste of time. There is no manual trans or 99.99% of drivers who can change gear faster than an automatic can, nor miss a gear, or over-rev, or be so consistent.
If you want to change gear fast in a manual trans car, you shouldn't lift off the gas, and you need to kick the clutch in and slide your foot off the side of the clutch, then be prepared to do that again (successfully) two or three seconds later.