It will work that way.

However, you have not understood what is happening. That's o.k.
You can use the water model to explain electricity. The battery under the hood is like a bath tub. When you switch something ON some water gets drained from the tub. The alternator is your spring and it will top off the tub. Then throughout the electronics of the car there are little pools of water (capacitors) that support the computer chips. So when you disconnect the tub you disrupt the water flow. But there are still these little pools that keep the memory chips going. These pools will drain after 20 minutes or so. You can drain them faster by turning ON a devise such as the brake lights. They won't light up, but they will dry up the little pools everywhere.
When you are done you can reconnect the tub. And that is good because the tub is still full. Now the little pools can fill up again, the computers start over and you can start the engine with your key.