> Did this replace the current .backup-running file?

No.

> Also, "still" running? What's the difference between is_backup_running and is_backup_still_running? (I think the former is cleaner)

I don't see a `is_backup_running` method. The existing check in the plugin (of which there is only one, `get_backup()`) reads the status from the `.backup-running` file. `is_backup_still_running()` is essentially a health check. I'm open to renaming, etc.