The system bleeds it out.
This kind of shows why I have used this method for decades and it has time and time again resolved issues that annoy me when it's not done properly. Noisy coolant flow through dash is one thing in some cars. Temperature fluctuations another. Anyway.
Eric The Car Guy knows what he is doing enough as a qualified mechanic, to use as a reference.
Bleed screw is used, but not sufficient to fully do the job. He only shows at the end, for a second, how much air was still in the system after a service on it.
I fill further and run the car through until all the large air bubbles are out and it only gets fine air bubbles every now and then. The system will continue to bleed that trapped air without drawing in significant volumes of coolant leaving it in a deficit or letting air back into the system.
The bleed screw on the VZ is on the top right corner, on the back of the radiator. I don't even use it. I did use it on the VP but only as a guide to know it was tight enough and leak free.
To quote Holden: "
Under normal operating conditions, the cooling system should not be topped up at the coolant filler cap"
Also, Holden description of the Alloytec system:
Coolant Recovery System
The coolant recovery system consists of a plastic coolant recovery reservoir and overflow hose. The recovery reservoir provides an air space in the cooling system that allows the coolant to expand and contract. The coolant recovery system provides a coolant fill point and a central air bleed location. It is partially filled with coolant and is connected to the radiator fill neck with the overflow tube. Coolant can flow back and forth between the radiator and the reservoir.
In effect, a cooling system with a coolant recovery reservoir is a closed system. When the pressure in the cooling system gets too high, it will open the pressure valve in the pressure cap. This allows the coolant, which has expanded due to being heated, to flow through the overflow hose and into the recovery reservoir. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum opens the vacuum valve in the pressure cap, allowing some of the coolant in the reservoir to be siphoned back into the radiator. Under normal operating conditions, no coolant is lost. Although the coolant level in the recovery reservoir goes up and down, the radiator and cooling system are kept full. During vehicle use, the coolant heats and expands. The increased coolant volume flows into the recovery reservoir. As the coolant circulates, any air that is present in the cooling system will accumulate at the pressure cap as this is the highest point. When the pressure cap releases it is the air which is expelled first. When the systems goes into vacuum it will suck coolant back in."