I always set up every system with an UID=1000 administrator user. I also manage sudo access by creating a sudo group, uncommenting the sudo line in /etc/sudoers, and adding users to the sudo group as needed.
On playing with my first Antergos install I noticed that the initially created user, administrator, has sudo privileges even though the wheel group isn’t uncommented in the /etc/sudoers file and the user isn’t listed directly, either. How is this administrative user (i.e. the user created on install) getting sudo privileges?