As someone said, Boeing flight manuals are strictly on a 'need to know' basis. I guess the type rating would take about 3 times as long if we knew everything about everything. Pilots know a little about a lot, if you know what I mean. I certainly had to learn a lot of different stuff, from how a jet engine works, to the toilet flush motor!! Saying that, I think it says it all that the chapter on our engines is about the smallest in the book.
I love the way that there is actually a big arrow pointing forward on the thrust lever quadrant saying 'Increase Thrust' - Duh!