I would be very surprised if this person did not have an "avoidant" attachment type.
I think you underestimate how severe the trauma of feeling disconnected from other humans can be.
I think the authors blog post conveys that he hasn't come to terms with the idea that "Wherever you go, there you are."
Social alienation is very bad, but is not severe trauma. Severe trauma would be something like being held in solitary confinement for months.
Voluntary social alienation can definitely be caused by trauma, I think that's what the person your reply to implied
Because of this, childhood trauma is a sort of universal explanation that will explain things even outside of psychology, everything from wheat allergy to male pattern baldness. You bet there's trauma in there somewhere causing it.