[development] Core modules group

[Cog Rusty]

In a Drupal 5 installation I noticed that the "optional core modules"
group in /admin/build/modules included the xstatistics and
comment_notify modules. The latter even included a link to its sponsor
in its description.

Apparently they both contain "package = Core - optional" in their info
file. Is this a normal practice?

I was already a bit confused by where some modules were placing
themselves in the navigation menu, and this came up like a violation
of a last asylum.