The problem with this analysis is that for psychologists, you can't make this analysis without an interview of sorts. As someone in the field, even if I think his behavior is bizarre, I would not feel comfortable making any statements about competence or ability to function. Below from the American Psychological Association ethics code.
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9.01 Bases for Assessments
(a) Psychologists base the opinions contained in their recommendations, reports, and diagnostic or evaluative statements, including forensic testimony, on information and techniques sufficient to substantiate their findings. (See also Standard 2.04, Bases for Scientific and Professional Judgments.)
(b) Except as noted in 9.01c, psychologists provide opinions of the psychological characteristics of individuals only after they have conducted an examination of the individuals adequate to support their statements or conclusions. When, despite reasonable efforts, such an examination is not practical, psychologists document the efforts they made and the result of those efforts, clarify the probable impact of their limited information on the reliability and validity of their opinions, and appropriately limit the nature and extent of their conclusions or recommendations. (See also Standards 2.01, Boundaries of Competence, and 9.06, Interpreting Assessment Results.)
(c) When psychologists conduct a record review or provide consultation or supervision and an individual examination is not warranted or necessary for the opinion, psychologists explain this and the sources of information on which they based their conclusions and recommendations."
You're hearing a lot more about the diagnosis stuff from psychiatrists who have (arguably) less expertise in diagnosis. Their training focuses more on the biological influences of behavior.