I have to call BS on that broken seat article.
Agreed. The author seems to imply that the violent pitch-up caused a massive g-force directed backward along the fuselage, which is clearly nonsense.
In such manoeuvre the g-force would be directed mostly
downward, towards the floor of the aircraft, i.e. no sliding back. Instead, head slumping forward, especially if the seat belts were not fully taut.