Stored procedure does not return correct result

I have a stored procedure like this

CREATE OR REPLACE PROCEDURE schema_name.CHECKS
IS
   tbl_name        VARCHAR2 (50);
   constraint_nm   VARCHAR2 (100);
   CURSOR cur_constraint
   IS
      SELECT DISTINCT table_name, constraint_name
        FROM all_constraints
       WHERE     constraint_type = 'R'
             AND STATUS = 'ENABLED'
             AND R_OWNER = 'owner1'
             AND r_constraint_name = 'constraint1';
BEGIN
   DBMS_OUTPUT.put_line ('Constraint Name');
   OPEN cur_constraint;
   LOOP
      FETCH cur_constraint
      INTO tbl_name, constraint_nm;
      EXIT WHEN cur_constraint%NOTFOUND;
      DBMS_OUTPUT.put_line (constraint_nm||'~~'||tbl_name);
   END LOOP;
   close cur_constraint;
END CHECKS;

And I execute this procedure by

set serveroutput on

BEGIN
   schema_name.CHECKS ();
END;

And the output I get is

Procedure created.
Constraint Name
PL/SQL procedure successfully completed.

It's not returning any result but ideally it should be returning a row (the select query used to define the cursor will return a row).

When I execute the above code as a PL/SQL Block like this

DECLARE
   tbl_name        VARCHAR2 (50);
   constraint_nm   VARCHAR2 (100);
   CURSOR cur_constraint
   IS
      SELECT DISTINCT table_name, constraint_name
        FROM all_constraints
       WHERE     constraint_type = 'R'
             AND STATUS = 'ENABLED'
             AND R_OWNER = 'owner1'
             AND r_constraint_name = 'constraint1';
BEGIN
   FOR i IN cur_constraint
   LOOP
      EXIT WHEN cur_constraint%NOTFOUND;
      DBMS_OUTPUT.put_line (i.constraint_name||' is in '||i.table_name);
   END LOOP;
END;

It is returning one row as expected.

Please help me understand why it is behaving strange when the logic is same except the way I execute it.

---

ALL_CONSTRAINTS is a bit like a mirror. Every user will see something different in there based on grants to that user. When executed as a DEFINE RIGHTS stored procedure it shows only what the owner of the procedure can see as a result of privileges granted directly to the owner (not through a role).

When executed as an anonymous block, it will show what the running user can see as a result of privileges granted to the user directly OR through a currently active role.

An invoker rights stored procedure (google AUTHID CURRENT_USER) will show what the invoking user can see as a result of grants to the user directly or through a currently active role.