If you don't have wired networking configured, fw_update(1) won't be able to fetch firmware on first boot, in that case it needs to be run manually.
The timezone and a default user can be created during installation, however yes, it is perfectly acceptable to expect that a user is capable of reading documentation.
It is not perfectly acceptable to claim "just works" if the user has to read documentation. It violates the definition of "just works" if you have to crack open the docs.
Yes, any task you have to read documenation for is, pretty much by definition, not a "just works" task. Of course, 'using' an operating system has so many aspects to it that your point is pretty nonsensical. In any case, we were talking about installing the OS, not using it.
That said, there are several OSes out there that have plenty of users who never read the docs for using it. Android, iOS, OSX, and Windows all have teeming masses of people who are able to use them adequately without reading documentation (just ask someone who's worked a support desk).
The timezone and a default user can be created during installation, however yes, it is perfectly acceptable to expect that a user is capable of reading documentation.