It depends where you are for local protocol but it has become unpopular to include intrusion other than the passenger compartment.
The idea that deformity elsewhere in the car was related to the amount of force exerted is outdated thinking of big cars with all steel frames and no crumple zones. To have significant intrusion on cars of the 60's, 70's, and 80's meant significant energy.
Now, not so much. Only the passenger cage is meant to not be deformed, everything else is meant to crumple and break off and absorb the energy of the collision first, before the patients bodies do.
So... you question is subjective. On older model cars without modern safe construction if I see a foot and a half to two feet of intrusion I'm going to strongly take that into consideration. But if the scene is a brand new, super safe, designed to spin and roll and crunch and absorb energy, I'm only going to look at the passenger compartment. Like all things in medicine that they write in the book as if it's black and white is actually a grey area.