Except, the big problem with doing that is that the car will not know that it now has a new battery installed, nor will the car know what the characteristics of the new battery are.
Even if you are swapping out one battery for the absolute EXACT same new battery, you need to recode so the vehicle knows the battery is new.
Agree. The car’s battery management system (BMS) monitors the state of the battery and adjusts the charging rate as the battery ages. When you replace the battery, if you don’t code the new battery to the car, the rate of charge applied by the BMS will be at the level that was required by the old battery (i.e. higher than is needed by the new battery) which could shorten the life of the new battery.