AWS Elastic Beanstalk - Why does a leader_only command on non-leaders output as an error?

Question

I have a container command for migrations with the leader_only argument set as below.

container_commands:
  01_reload_nginx:
    command: "service nginx reload"
    ignoreErrors: true
  02_setup_env_vars:
    command: "./bin/setup_env_vars.sh"
  03_django_migrate:
    command: "./bin/migrate.sh"
    leader_only: true

When the deployment script runs on a non-leader instance the 'postbuild' script logs an error in cfn-init-cmd.log. Here is the output:

[INFO] ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[INFO] Config postbuild_1_Latner_Test
[INFO] ============================================================
[INFO] Command 01_reload_nginx
[INFO] -----------------------Command Output-----------------------
[INFO]   Redirecting to /bin/systemctl reload nginx.service
[INFO] ------------------------------------------------------------
[INFO] Completed successfully.
[INFO] ============================================================
[INFO] Command 02_setup_env_vars
[INFO] Completed successfully.
[INFO] ============================================================
[INFO] Test for Command 03_django_migrate
[ERROR] Exited with error code 1

The leader instance runs as expected with the command output plus a 'Completed successfully' message. The error will become an issue when detecting errors during deployment

Why is it that the cfn-init-cmd.log outputs a error code 1 when a non-leader checks if it needs to run the command?