Creation of assessment tools without research and validation?

I want to be vague so that anybody who may know me wouldn’t recognize this.

I’m in a position where a coworker/(role of supervisor in general but only partially? it’s weird) with a degree higher than mine (a masters) yet one that requires and includes 0 research (I think you know which one) is stating that she has formulated her own assessment tool that results in the juvenile diagnosis of a pretty heavy lifelong diagnosis (think things you typically would not diagnose kids under 16-18 with for a plethora of reasons). She developed this during education, testing on her own subjects/patients within a closed loop of that education cohor, no research, no published anything, it is not publicly available. This assessment tool is now being accepted at our practice as fully valid and will get “rolled out” to children we work with soon.

I’m genuinely confused because I was under the impression that assessment tools must be extensively regulated and validated through rigorous and appropriate research methodology, and typically have subsequent publications regarding application, results, interpretations, limitations, etc of said assessment tool. I’m uncomfortable at the idea of some of my patients being subjected to invalid testing with resulting shared diagnosis of something that, if true, does impact them for life. I mean, even being improperly diagnosed can be borderline traumatic for people.

What am I missing here? Is this something I’m simply not aware of, personally contrived and designed tools developed on small and somewhat uniform private populations which are then applied in other settings with no background, data, research, validity?