I don’t remember any instructions coming with any Mac I’ve bought I. The last decades. The license/warranty info sure, but actual printed documentation is limited to a couple pages of to plug stuff together.

Print instructions would get outdated with each OS release. But they do have comprehensive online instructions which do cover how to maximise windows.

https://support.apple.com/en-gb/guide/mac-help/mchlp2469/mac

In addition, macOS and iOS come with a “Tips” app (yellow with a lightbulb icon) which covers several topics.

The Help menu bar item must be the most overlooked (under-looked?) part of Mac OS in history. it’s always there, never used!

What they’ve done with the CMD-? keyboard shortcut that nobody knows about has to be the most brilliant UI that nobody uses.