Design docs and drawings obviously (easily 1k pages more if you fit it on a4), since each trade needs it's own views. Specifications are included, as a legal document that calls out which regulations every possible system will follow and calls out exceptions (proof they apply). All possible testing from receiving it (and documentation including pictures), proof of setup, proof of commissioning (IE construction essentially needs to do what a tech bro would do with automated testing, by hand with with each step documented and signed for, and each possible state the system could be in). Any other type of test report NETA/material quality/thermography/whatever (a single breaker easily comes to two pages of test report, a voltage/current meter easily comes to three pages per phase). Pictures are likely kept to only two per A4 page.
Basically it's a "declaration from ignorance", since big numbers sound scary and wasteful to others who haven't worked in the field.