How do I audit GRANT on UTL_MAIL by SYS user?

My goal is to monitor the audit trail (unified_audit_trail) for grants to and revokes from UTL_MAIL by the SYS user. So far, I have not been able to see these actions in the audit trail. Here is the setup:

--Database is set to use pure unified auditing and is working/logging.

--Create policy for watching for grants on UTL_MAIL
create audit policy pol_utl_mail_grant
ACTIONS GRANT
ON UTL_MAIL;

--Now enable policy
audit policy pol_utl_mail_grant by SYS;

--See policy enabled
select * from audit_unified_enabled_policies;

--Provoke action to trigger audit action