The Scope of "AUDIT POLICY XXX"

When you issue the very simple unified audit without any modifiers like this:
SQL> AUDIT POLICY ORA_DATABASE_PARAMETER;
The scope of the audit seems to be very vague and unpredictable, because it misses BY (or EXCEPT) and WHENEVER.

Let's go back to Oracle 12c documentation AUDIT (Unified Auditing) and see the definition.

If you omit the BY and EXCEPT clauses, then Oracle Database enables policy for all users.
...
If you omit this clause (WHENEVER), then Oracle Database performs the audit regardless of success or failure.

Now we know the answers, the above very simple statement audits ALL users and whatever the alteration on database parameters is SUCCESSFUL or NOT SUCCESSFUL.