You'll find plenty of failed seats in crashes, it's a known factor and an item that has had it's share of recalls. I'm sure you can find many improperly or poorly positioned seats that also contributed to the post accident conditions.

Those failures are usually cases of "big man in small car gets rear ended" not frontal collisions. Frontal collisions almost never break seats. Humans don't rebound that hard.

Unfortunately, I've seen first-hand that passengers in the front of a vehicle can be thrown into the rear of a vehicle in a crash. The way that excerpt describes it though, it makes me wonder if they tried to crawl out of the car "post crash" via the rear, and checked out before they could get out of the car?

the commenter said "tossed", the NTSB said "moved". there was no speculation as to why.

The sentence's grammar is vague. The "was" might have been meant to apply to both clauses, so that the driver "was seated" at the time of the crash and then "was moved" during the ensuing mayhem. Or he crawled into the back and died.

The NTSB might have been trying to use neutral language for uncertain events, like how "the position changed" could mean intent or just a force of nature. I don't know what the right interpretation is.

I've been in a crash as passenger in front.

It's surprising how fast I got out of the car via back seats without even thinking.

(only thought was - door on my side is potentially blocked, get out...)