I'm Neal and I am here to assist you. Only accept when you are happy with my assistance. If I can't help I will open your Question to other experts.
What did the article you read state? And where did they get their information?
Besides being a mechanic which is the family business I also have been a firefighter paramedic for over 20 years and have seen more accidents than I can even remember, and I agree based on my experience that the safest place for an unrestrained dog would be in the floor board. Of course nothing is 100% but a dog in the back seat is either going to be ejected or thrown forward into the windsheild and dash area, the front seats will usually not stop them from flying all the way to the dash in a head on collision.
Again this is based on my experience and is not based on any scienticic study, this is just what I have seen from real world experience with accidents with and without dogs involved.
With all due respect, to the car expert, the safest place for a dog depends on the size of the dog. An unrestrained dog on the floorboard of a car is more likely to recieve blunt force trauma to the body, which can be fatal to dogs.
A medium or small dog should be in a crate/kennel in the middle of the backseat or restrained in a dog-approved seatbelt/harness. There are literally thousands of possible ways to restrain small to medium sized dogs in a car that range from the inexpensive harnesses to more expensive metal sided crates that bolt into the car itself.A large dog should be restrained in the kennel in the backseat or in the cargo part of a van or SUV.
Dogs on floor boards get killed either due to impact or injury from the car being out of control. Additionally, the person driving the car can be injured due to the unrestrained dog flying about the vehicle during an accident.