I’m a little confused. The article seems to walk through reinstalling Mac OS 9.1, or performing an erase and install. And this sounds like upgrading as opposed to updating.

Upgrading is going from one major version to the next. There is a higher risk of failure when doing so.

Updating is increasing the minor version, including bug fixes and small patches.

I am sure I was one of those people who upgraded their machine from 9.0.3 or 9.0.4 to 9.1, and I do not remember batting an eye doing so. By this time, updates were readily available via the Internet — this should have been a fairly straightforward process, without the need for CDs or multiple hard drives.