SQL & PL/SQL :: Conditional Predicates Is Not Working With MERGE

I realized that in statement level trigger conditional predicates(INSERTING, UPDATING & DELETING ) are not working.

For example please run below sql:

create table merge_test(col1 number, col2 number);
create or replace trigger merge_test_tr_stat
after INSERT OR UPDATE OR DELETE on merge_test
begin

if inserting or updating or deleting then
dbms_output.put_line('conditional predicates is working ');
else
dbms_output.put_line('conditional predicates is not working ');
end if;
end;

set serveroutput on;
insert into merge_test values (1,1);

Output
------
1 rows inserted.
conditional predicates is working
conditional predicates is working

set serveroutput on;
merge into merge_test mt using ( select 1 col1 from dual ) tab
on ( mt.col1 = tab.col1 )
when matched then
update set col2 = 2
when not matched then
insert values (1,1);

Output
------
1 rows merged.
conditional predicates is not working
conditional predicates is not working

How to use those conditional predicates in statement level trigger.