The person who wrote it probably gets measured on the amount of "work" he/she produces.
The more detailed the tutorial, the more "work" he/she has accomplished, at least according to the rules/processes internal to the department in Amazon.
The person writing the tutorial has to make it extra complicated. Otherwise she/he will lose her/his job because other documentation writers will do a "better job" by writing more "detailed" tutorials.
I think many of us spend a lot of time in our ecosystems and we might lose sight of what's outside. If someone spent all their days writing complicated Aspect-Oriented code then maybe to them this is just second nature and the right way to do it. What if you wanted to add more features, after all?
I wouldn't go so far as to imagine perverse incentives from management. It could just be a cultural bubble that the person works in or they could work in a place where most problems are far more complex and these sorts of solutions make sense.
It can be difficult to remember who your audience is, what they know and what they need to be told.