> something like ABS, it should detect your emergency stop and provide the most effective stop the car is capable of.
That's not what ABS does, ABS just cadence brakes for you only it's able to detect when a wheel loses grip and stops that wheel actually braking until there is a chance to regain grip when it will re-apply the brake effort. A proper ABS system should be able to do this many times more quickly than a human driver.
What you sound like you are describing is emergency brake assist where the computer decides you are doing an emergency stop and then takes over and brakes as hard as it can, relying on an ABS system to avoid locking up the wheels and loosing braking efficiency. The idea is that often drivers don't brake hard enough or scare themselves at how violently the car brakes when they do hit the peddle hard that they back off and don't slow enough to avoid hitting things.
Emergency brake assist systems can be a total PITA. The Mrs' Merc has this and if you move your foot too quickly from the accelerator to the brake peddle it guesses you're emergency braking and tries to pull a full blown stop. So unless you're careful you find the car doing crazy things while you drive moderately quickly down country lanes, where it is normal to move your foot quickly but only apply minimal pressure. Once the stupid computer has got it into its tiny mind you want to stop you have to completely remove you foot from the brake peddle before it will give you control of the car back.