Why disallow package within the class name?

This can be generalized.

For example, people tend to name git branches with something like "BugID1854286_fix_pointer". Whe GitHub (or whatever version control) shows you branches, it show you a prefix of the longer branch name, so people have only 6-8 human readable characters in the branch pull down, and they're all at the end of the strings so displayed.

The they title the PR "BugID1854286". The PR intro often consists of a phrase like "Fixes BugID1854286". That same phrase just might occur as a comment in the changed source, as well.

The justification given is usually "it aids tracking bugs", but that's false, GitHub (or whatever substandard corporate crap like Serena Dimensions) does the tracking on some internal ID. Branch name and PR title are for humans. Also, got branches are ephemeral, so who cares what the name is?