I haven’t changed a thing. I’m going to have a look into the archlabs-image which I used to install my system. I know that the shasums were correct and I very probably downloaded it with Transmission/Bittorrent, which in itself should garanty integrity of the image as long as one can trust the magnet-link on sourceforge.
The USERGROUPS_ENAB from the /etc/login.defs comment, does:
Enable setting of the umask group bits to be the same as owner bits (examples: 022 -> 002, 077 -> 007) for non-root users, if the uid is the same as gid, and username is the same as the primary group name.
This also enables userdel to remove user groups if no members exist.
The reason you’re getting the “users” group is in /etc/default/useraddI think
# useradd defaults file for ArchLinux
# original changes by TomK
GROUP=users <<<<<<<<<<<<<<<<< Here
Is there a new group created for you’re new user matching username, and have they been added to it?
It’s worth noting we don’t change any of this stuff, just using the Arch defaults for basically everything that doesn’t need to be changed for install (keyboard, time, locale, etc.).