Look, computers are like idiot savants - incredibly fast and capable of doing all sorts of things with mindless determination, but without a shred of common sense - so when you’re programming you have to literally explain everything including what for you is obvious and there is a whole class of bugs (around corner cases and boundary conditions) related to the programmers not explaining absolutelly everything and forgetting some really rare or unusual situations.

For documentation purposes one should assume that at least some users are like computers, without the savant part.