As the gasket fails, it might first fail to where the higher pressure combustion gas blows into the cooling jacket. That's why it will force your coolant out of the radiator into the reserve tank.

Once it's really good and blown, and after you refill the rad, it will also suck coolant into the combustion chamber on the intake stroke....the coolant burns and smokes white......Or, once the engine is stopped, the pressure in the cooling system will force coolant into the now depressurized cylinder where the gasket is blown or head is cracked, and then it will smoke when started and also blow into the radiator.

For the guy with the blown HG on the7mge....that's a common failure for that engine....It ain't no cheap fix when compared to the 22re. So you really should do some homework before you do it or have it done to make sure it stays fixed.