Reading https://www.php.net/manual/en/function.openlog.php , it’s not possible to keep 2 connections open to syslog with a different tag.
So this is a limitation of our log system, it’s not possible to use syslog for both normal logs and audit logs with different tags.

Not sure if it is possible to fix this without losing performance, but this limitation could be explained in our logging documentation.
https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/logging_configuration.html