Comment by Volundr

I was responsible for administering a self hosted GitLab instance for a medium sized company and our backups never required downtime. The built in backup command doesn't require downtime but also isn't a consistent point in time snapshot (specifically because the instance keeps running while the backup is being taken). If they've decided they need one for some reason, stopping GitLab is certainly the easiest way, but not the only way of accomplishing that goal, but that'll be true of any self-hosted forge, including GitHub.