These "mental health experts" aren't stupid: Deny a patient the right to own a weapon and they sue if they are unable to defend themselves in an emergency. Fail to deny a patient the right to own a weapon and their victims sue them for doing so.
It is a no-win situation for them. Therefore, as the "experts in the field" they deny the linkage exists.
Problem solved.
Their bottom line....I don't want to get involved....just collect my big fat paychecks.
You know damn well the theatre killer told his shrink of his plans...and she just sat on it.