How to get file-based auditing of logon/logoff in mixed mode

Hello,

I have been asked to enable logon and logoff auditing of regular users on a 19.14 database.
I need it to be file-based.

It's configured by default i.e. in mixed mode.
I have set:
audit_file_dest string /app/site/<SID>/base/adump
audit_sys_operations boolean FALSE
audit_syslog_level string
audit_trail string OS

The following traditional audit setting works OK:
SQL> audit session;
I do get the *.aud files in adump.

However if I try using the new style auditing after clearing the former setting by "noaudit session":

SQL> create audit policy connection_policy actions logon, logoff;