My reading of that documentation doesn't lead me to believe that the intention is to share the
sudo group. It appears to me that the developers chose 27 because it was unused on their system, and that the intention was to create a new
mysql group of GID 27. That belief is undermined by their addition of the
-o flag to
groupadd, though, as that explicitly allows a new group to share an existing GID, which would not be in the interests of separation of duties, and thus not of security.
If it was me, I would allow
groupadd to select the GID; I'm not sure whether a system GID (one less than /etc/login.defs:GID_MIN) is required.
groupadd -r mysql
and then refer to the group with the
mysql name and don't rely on the GID being 27. A quick search of that doc for "27" doesn't come up with any matches other than the page you already found. There are no results for
chgrp, and the only hit for
chown is in the Post Installation Setup where they use the group name in:
chown mysql:mysql /usr/local/mysql/mysql-files
chown mysql:mysql /usr/local/mysql/data
(I've adjusted the commands to show the full paths versus the relative ones from the doc).