Audit grant object privileges for all uses include sysdba

I set audit_trail=DB and audit_sys_operations=ture, this allow me to audit sysdba to grant object privileges, I can find the inforamtion in audit_file_dest

Then I login as sysdba, SQL>audit grant any object privilege by access; Then I login as normal user to grant select on xxx.test to userid, later I view dba_audit_trail, I can't find anything there.

Unless I run <audit grant on xxx.xxx by access> on the specific table, then I can find this in dba_audit_trail.

Is there anyway to audit all the users' grants?

Thanks,