That's a reference to this incident, reported by Richard DeMille in the "Barefaced Messiah" interviews:
We got in a little aeroplane and flew to Phoenix and then flew to Chicago, where Ron proceeded to be interviewed by a psychiatrist and psychologist. He wanted to establish an answer to her [Sara's] charges that he was, in the words of a psychistrist who hadn't even seen Ron, a paranoid schizophrenic. He wanted a testimonial from a professional who would say he was OK.
He and I together went to the psychiatrist. It was a short interview, the psychiatrist didn't like the smell of it and thought he was being manipulated so he made a few psychiatric noises and nothing much came of it. We paid him $10 and left. Then Hubbard went to Murray Krout, who was a prominent diagnostic psychologist of that era. He did projective testing , Rorschach tests and that kind of stuff, of Hubbard and said he would send a report. The report he sent later was very bland encouraging, man of creative talent who is upset by family problems and dissension and so forth depressing his work... an upbeat harmless report. The main value of it to Hubbard was that it didn't say he was crazy. He claimed he had been given a clean bill of health by the psychiatric profession. He was pleased with it.
https://www.cs.cmu.edu/~dst/Library/Shelf/miller/interviews/demille.htm