Some people have learning disabilities, and abnormally high native symbol processing skill is on the list.  The QuasiGreatTeacher is someone who, due to this learning disability, is incapable of communicating with his peers well enough to understand when they have already had "his" ideas before him.  Consequently he must struggle mightily to put them into different words, simply to resolve his confusion that they are "his".  The effort of unnecessary re-invention produces a set of descriptions with large secondary value, i.e. to unrelated third parties who are looking for a clear exposition.

''A lot of classic spiritual texts have been produced this way. Basically, the stupidest but most dogged disciple, if he has a neurotic habit of writing things down, will make the best teacher for the third and subsequent generations.''

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I really wish I understood the first sentence of the first paragraph.

''It's homage to the modern myth that every "disability" is actually "being differently abled": being too skilful in some sense.''

It's another way of wording the old put-down "so and so has an IQ of 150 ... and he's missing the first hundred."  See the mild controversy over edits in the StephenWolfram page.  Never mind the strawman myth described above; surely you can't naively equate "learning" with "symbol processing skill"?  Think of the successful college athlete who has gotten by on size and speed, who then washes out at the pro level because of bad technique.  Well, many "major" scientists have severe collaboration problems -- analogous to portions of sports technique -- that are not readily recognized because they are so common among scientists that there are compensatory Patterns.  A writing style which justifies a pompous lack of crediting others, is one of the most obvious such Patterns.