His mother was killed in a catastrophic car chase so I can imagine that he is a little over-sensitive and triggered by anything that remotely resembles anything like that. He will not view things in the same way that some one who has not been affected by such things will. Although he was not with his mother when she died, I can imagine he will feel situational anxiety.
45 years ago, I was involved in a very bad accident outside my parents' house (a car driven at great speed went into the back of mum's car). My anxiety when I have to make that turn even now is dreadful and if there is nothing behind me to have seen me slow down and indicate, I will drive up the road, turn round and come back for fear of an unseen speeding vehicle to come round that corner. It is completely irrational.
I do have immense sympathy for him regarding anything like this. However, when one adds it to the catalogue of other whinges (some of which might depend on varying recollections) I can well understand how it might be seen as just more Sussex "cry wolf, attention seeking, snowflakery, me me me, money making" histrionics.