This test is actually fairly well validated. The purpose isn't to specifically diagnose your problems, it is to find the floor for how much trauma you may have experienced. Sure, some may have had parents under the influence occasionally while others witnessed heavy usage in front of them. The point is that even for the "light" case, that is a significant issue.

Think of it as childhood trauma triage. It is a good first pass to help people understand their past and maybe help some people understand that their past is more traumatic than they realize.