[Spearchucker]

The people using my system never skim my document. Lawyers tend to scrutinize it. As for the document being a war-and-peace epic yes, this happens. Mostly because people cannot write technical documentation. The hugest system can be distilled down to a single diagram which should require no words of explanation.

By way of example - here's a conceptual design for an insurer wishing to participate in a panel of protection providers.

https://www.wittenburg.co.uk/images/consulting/conceptual_de...

If you're in this world all of it is self-evident, none of it a surprise, and you understand the flow. That document leads to other more detailed designs that each address one distinct rectangle in that image.

At some point all of this will become a specification. Again the immensity of that depends on the ability of the authors. On their ability to manage complexity, and their skill as technical writers.

Either way yes, when the wheels fall off that document becomes the truth, the one everyone goes to to settle disputes. And with a capable team it never gets to that because the documentation is succint and agreed to, and what is delivered matches what was specified.