usermod: cannot lock /etc/passwd, but user is in root group which owns file

As the title says. Interesting behavior. I just switched over to nologin on root user for security, after adding my user to root and sudo groups. I added a longer sudo timeout as described in the link below. So I should be able to use usermod without adding sudo because root owns /etc/passwd and user is part of the root group..no?

https://unix.stackexchange.com/questions/26074/is-there-a-way-to-stop-having-to-write-sudo-for-every-little-thing-in-linux/676564#676564

Also, two more problems I found, likely related.. using guestmount failed from permissions, so I added user to kvm group (owner of the complaining file), but still requires sudo. Also, once mounted, I tried ls to /mnt, but have to use sudo even though /mnt is root:root..?

This isnt a trivial problem, because nologin on root disables most brute force ssh attacks, and yet having to use sudo before things like ll disables any alias.