Syslog setup but still logging to seafile logs

Seafile CE 6.3.4

I’ve configured the seafile.conf and 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?