SYS_REFCURSOR returns incorrect number of rows ?

Looping thru a SYS_REFCURSOR leads to one more result than expected. With one doulet.

EXAMPLE: (happens in all of our databases, standard DBs, CDBs, PDBs, on Solaris, Exadata ...

CREATE TABLE TEST (NUM NUMBER);

INSERT INTO TEST (NUM) VALUES (1);

INSERT INTO TEST (NUM) VALUES (2);

COMMIT;

DECLARE

 result  NUMBER;

 CURSOR  cur_std IS SELECT * FROM TEST;

 cur_ref SYS_REFCURSOR;

 c_sql  VARCHAR2(99) := 'SELECT * FROM TEST';

BEGIN

 FOR x IN cur_std

 LOOP

  DBMS_OUTPUT.PUT_LINE(x.num);

 END LOOP;

 DBMS_OUTPUT.NEW_LINE;

 OPEN cur_ref FOR c_sql;

 LOOP

  FETCH cur_ref INTO result;

  DBMS_OUTPUT.PUT_LINE(result);