why past perfect for the firs example and past simple for the second one

Question

I saw this girl when I was parking my car last night. She was crying. She explained she had a terrible fight with her boyfriend while he was giving her a ride home earlier, which ended in his pulling over and forcing her out of the car.

Eventually I lowered the window and he said: 'Hi, can you help me . I took the risk. He explained to me that while he was driving they had had a terrible argument and that he had decided to get out of without thinking that it was raining and that he was far from any town or village.

I really don't understand why in the first example it is past simple and in the second one it is past perfect . For me both situations happened before the explanation and should be past perfect and the argument was completed at the time of the explanation

Answer 1

You can use past tense when talking about a past action.

You can use past perfect when talking about an action that occurred before a certain time.

So in many contexts that you can past perfect, you can also, grammatically use simple past.

In the first example the past perfect would be quite natural. The writer is describing the events when he saw a girl, so when reporting her speech it would be very natural to backshift: "She explained that she'd had an argument..."

Likewise in the second, past perfect is natural. "... while he was out driving they'd had..."