Earlier quoted context omitted.
How can you be so critical of a stranger's work given that you haven't even seen it? "that reason was most likely because" -> Bear in mind you do not actually know the given situation.
None of us knows the exact situation but the fact that the person said his documentation was "complete, correct, and relatively terse" is a red-flag. It seems to me like smug over-confidence. If the document really was so clear and error-free, then why would the boss try to "fix it"?
People often apply nonsensical standards to things.