Awesome! I had missed this thread.  I've read a few of his enneagram books and watched many lectures. I always typed him as NiFe.  🙂
Naranjo tried to link the lowest unhealthy potentials of Enneagram types with DSM psychological disorders just to get it more credence in the psychiatric field. To use an example, he linked 5 (his own type) to schizoid personality. He didn't believe that all 5s are schizotypal, but rather, that 5 at its lowest and darkest potential would match some of the patterns of schizoid people.  He linked each type to a few other models, including MBTI, to try to illustrate the nature of the types in terms that people were already familiar with.
The fathers of enneagram were Ichazo and Gurdjieff.  Gurdjieff steered away from doing "Enneagram of Personality" because he felt the public wasn't ready for it.  Ichazo started slowly working out his enneagram of personality and writing about it, and taught some people in the Arica school, including Naranjo.  But his work was not close to ready and Naranjo jumped ahead in publishing his own regardless.  Ichazo was a self-proclaimed 9 and Naranjo basically cuckolded 9, taking any life and interest out of the type in his work. He made a few other mistakes, like mixing up Sx 4 and Sx 6, but later on he corrected many of those publicly. However, as far as I know, he never addressed the problems with 9.  In my enneagram community we joke that he had "daddy issues" directed at Ichazo.  This mistreatment of 9 carried over to Riso & Hudson, who painted 9 in a very 1-dimensional light, which caused many 9s to mistype as 4 and 5.  Riso himself was a very obvious 9 with a four fix who mistyped at 4, due to Naranjo's cuckolding of type 9.  So that problem set off an endless trend of bullshit in the enneagram community. Whereas Naranjo's 9 was basically a dead fish, Ichazo's 9 was called "Over-nonconformist."
That said, Naranjo is generally well respected among enneagram elites, and personally I hold his work in much higher regard than Riso & Hudson, who are basically plastering descriptions on types that remind people of "internet astrology memes." This washing out of the real meaning, and removal of even the SINS, the basic structure of enneagram, has caused mayhem in enneagram communities, with 85% of people on the board where Russ Hudson participates, typing at 4 on their poll for "what's your main type?"   This is consistent in other communities who are steeped in RH and their teachings.  Those who go back to Naranjo and read ALL of his work - not just Character and Neurosis - usually have a deeper view of the mechanisms of the types. But one has to keep the comparisons to mental illnesses in perspective and read the introduction chapters in that book, which explain why he writes this book and that he's aiming for credence in the psychiatric community, not proclaiming that every person's type is a mental illness.  For this reason, it's not an ideal typing tool. But his later books elaborate more on the types themselves, without the mental illness component. He also publishes work that shows groups of people who were typed a certain way, all talking about their subtypes.  And there were many videos on youtube in the past, which now have to be purchased, where he elaborates on each subtype (as in Sx, So, and Sp variant for each type) and describes their major themes.
His work was an important step in the enneagram world, but some of his earlier books just came out.... too early. Not enough was known. Ichazo never got to finish all he wanted to do, however, so arguably someone had to pick it up even if it wasn't perfect.