That just seems weird (surprising!) for what is essentially a fender bender caused by human error with no injuries (not a comment on the amount of damage, just a completely routine accident). Was this because of their monitoring your Twitter, this website, or through insurance claim monitoring? I assume the letter makes it clear.
It’s certainly true that property damage could have likely been eliminated in this case with the right safety systems, and maybe that is what they are interested in? Maybe they are weighing cost/benefit of adding regulation to require such equipment, and gathering data to support that?