I don't know if it would eliminate it but it would greatly reduce the potential for that particular cause. My thinking has mostly been about whether she actually did hit a closed garage door and if so from inside or outside. I agree with another poster who said the firemen probably pulled that garage header down. I hadn't thought about that before.
...The reason they opened the roof on that fire was because they could not get around the car to get into position and extinguish it completely.
By venting above it (or trying to) the idea was it would not CONTINUE to spread into the house which had a door 6″ from the free burning car with a garage full of flammable liquids and access from the interior was difficult.
The fire was traveling the ceiling which shared a common joist space with the garage. By venting the roof they hoped to stop the spread of horizontal fire from taking hold of the structure before they were able to completely open up inside. The house had multiple rehabs and was very cut up in its interior construction making it hard to open up close to the wall/garage.
Sounds as if the poster was there and is very familiar with the fire. If this house had multiple rehabs it is very possible some things were not done to code. The fire was could have resulted from an undetected defect relating to faulty workmanship and reached the that morning.