I believe what they mean is that because this package is depended on by
so many other packages, it needs to be upgraded a bit differently. This
is done to prevent massive rebuilds for substitute servers and to
reduce the risk of breakage.

From: https://guix.gnu.org/manual/en/html_node/Submitting-Patches.html
=2D-8<---------------cut here---------------start------------->8---
more than 1,800 dependent packages
core-updates branch (may include major and potentially disruptive
changes). This branch is intended to be merged in master every 6 months
or so. This branch is not expected to be buildable or usable until late
in its development process.
=2D-8<---------------cut here---------------end--------------->8---

What I don't know, is the correct process is for this type of
submission.  I'm seeing a `core-updates-glibc-2.39` branch, but
presumably that is only for glibc; does one need special privileges to
create a new branch or do we just submit the patch based off the master
branch as a patch to a branch that doesn't exist?

=2D-8<---------------cut here---------------start------------->8---
git branch -a | grep -a core
  remotes/origin/core-packages-team
  remotes/origin/core-packages-team-old
  remotes/origin/core-packages-team-old2
  remotes/origin/core-updates-glibc-2.39
=2D-8<---------------cut here---------------end--------------->8---

v/r,

Aaron

P.S.
I just noticed that the latest version of the manual drops the package
number branch definitions; I'm not sure if this was moved to a
different section now; accidentally deleted; or if it is going to be
dropped as a requirement. See:
https://guix.gnu.org/manual/devel/en/html_node/Submitting-Patches.html
https://guix.gnu.org/manual/en/html_node/Submitting-Patches.html