Why startup audit file going to $ORACLE_HOME/rdbms/audit and not audit_file_dest

Oracle version 19.18.0.0

Linux 4.14.35-2047.514.5.1.2.el7uek.x86_64

Audit settings

SQL> show parameter audit

NAME                  TYPE     VALUE

---------------- ----------- ------------------------------

audit_file_dest      string    /u01/app/oracle/admin/BFS109L/adump

audit_sys_operations     boolean   TRUE

audit_syslog_level           string    SYSLOG.INFO

audit_trail              string    OS

unified_audit_common_systemlog  string

unified_audit_sga_queue_size      integer   1048576

unified_audit_systemlog        string

According to Doc ID 2584757.1

By default, the operating system files are in the $ORACLE_BASE/admin/$ORACLE_SID/adump directory 

...

you can change the location of this directory by setting the AUDIT_FILE_DEST initialization parameter.

But why is the startup audit file still going to