It wasn't that long ago, that the manual spelled out everything in detail enough that a kid could understand, absorb, and decide he was going to dive into his own and end up in the industry. I wouldn't have broken or created nearly as much, without it.
But, a few things challenged the norm. For many, many reasons, manuals became less about the specification and more about the functionality. Then they became even more simplified, because of the need to translate it into thirty different languages automatically. And even smaller, to discourage people from blaming the company rather than themselves, by never admitting anything in the manual.
What I would do for a return to fault repair guides [0].
[0] https://archive.org/details/olivetti-linea-98-service-manual...