Syslog setup but still logging to seafile logs

Seafile CE 6.3.4

I’ve configured the seafile.conf and seahub_settings.py for logging to syslog but it’s still writing out to the files in the seafile_home/logs directory.

For example, everything that is written to the controller.log file is now being written to the syslog file too (albeit in a slightly different format). I copied the setup exactly from the Seafile manual, including the
‘disable_existing_loggers’: True,

Is this a known issue or is the config a problem?

Thanks