[BUG] Centos 8: Adding root user to group with group.present gives false failure

Description
When creating a group and adding users with group.present if the user root is added Salt reports a false failure.

In my project I have a salt state that creates a group and adds an existing user and root to the group. Upon applying the salt state it fails at that specific state, stopping any other states that rely on it from running. However, if I look at /etc/group I can see the group and the correct users.

Setup
I have been able to replicate this with minimal config needed.

# top.sls
base:
  '*':
    - addUser
    - addGroup

# addUser.sls
test:
  user.present:
    - fullname: test user
    - home: /home/test

test2:
  user.present:
    - fullname: test2 user
    - home: /home/test2

# addGroup.sls
Backup users:
  group.present:
    - name: testgroup
    - addusers:
      - test
      - test2
      - root  # leaving this line out will let the state succeed, adding it will cause a false fail.

I am using a masterless set up with Vagrant handling the creation of the Centos 8 VM.

Steps to Reproduce the behavior
Run the Salt state either manually or using Vagrant.

Screenshots
I don't have screen shots, but this is output I get when I run the state Backup Users manually using -ldebug. This was run after the users were created.

*SNIP*
[DEBUG   ] LazyLoaded config.option
[DEBUG   ] LazyLoaded group.present
[INFO    ] Running state [testgroup] at time 05:14:04.441145
[INFO    ] Executing state group.present for [testgroup]
[DEBUG   ] LazyLoaded group.info
[DEBUG   ] LazyLoaded cmd.retcode
[INFO    ] Executing command ['gpasswd', '--members', 'test,test2,root', 'testgroup'] in directory '/root'
[DEBUG   ] LazyLoaded test.ping
[ERROR   ] {'Failed': {'members': ['test', 'test2', 'root']}}
[INFO    ] Completed state [testgroup] at time 05:14:04.823030 (duration_in_ms=381.883)
[DEBUG   ] File /var/cache/salt/minion/accumulator/140649583073656 does not exist, no need to cleanup
[DEBUG   ] LazyLoaded state.check_result
[DEBUG   ] LazyLoaded highstate.output
[DEBUG   ] LazyLoaded nested.output
local:
----------
          ID: Backup users
    Function: group.present
        Name: testgroup
      Result: False
     Comment: The following group attributes are set to be changed:
              members: ['test', 'test2', 'root']
              Some changes could not be applied
     Started: 05:14:04.441147
    Duration: 381.883 ms
     Changes:   
              ----------
              Failed:
                  ----------
                  members:
                      - test
                      - test2
                      - root

Summary for local
------------
Succeeded: 0 (changed=1)
Failed:    1
------------
Total states run:     1
Total run time: 381.883 ms

The final line of /etc/group:

testgroup:x:1003:test,test2,root

Versions Report

Salt Version:
           Salt: 3001
 
Dependency Versions:
           cffi: 1.11.5
       cherrypy: Not Installed
       dateutil: 2.6.1
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
         Jinja2: 2.11.2
        libgit2: Not Installed
       M2Crypto: Not Installed
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.6.2
   mysql-python: Not Installed
      pycparser: 2.14
       pycrypto: Not Installed
   pycryptodome: 3.9.8
         pygit2: Not Installed
         Python: 3.6.8 (default, Apr 16 2020, 01:36:27)
   python-gnupg: Not Installed
         PyYAML: 5.3.1
          PyZMQ: 19.0.2
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.5.3
            ZMQ: 4.3.2
 
System Versions:
           dist: centos 8 Core
         locale: UTF-8
        machine: x86_64
        release: 4.18.0-193.14.2.el8_2.x86_64
         system: Linux
        version: CentOS Linux 8 Core

Reproduce the issue with addUser.sls and addGroup.sls on CentOS 8, then trace group.present around the gpasswd --members command and its reported result. Done means adding root to testgroup returns success while /etc/group retains test,test2,root.