The essence of creating tension is setting up the possibility of something bad happening, and making the audience wait to find out what happens.
Is Ort’s dad coming home, or has he had a car accident? Tim Winton uses a false alarm (an approaching car) to make us think there’s an answer, and then makes us wait while he describes the environment.
Then he describes a new car, and stretches out the reveal again by not telling us directly what the news is.
So this is all about building tension by delaying giving answers, and delaying by focusing on other parts of the environment.