SQL & PL/SQL :: Grant Privileges To Subprogram Via Role - Should Not Work

I bought Selftestsoftware for 1z0-147 for 9i and 10g. Selftestsoftware is endorsed by Oracle, should be high quality.

But its below sample question and answer seem to be wrong: It says that privilege for subprogram can be granted via role. But from Urman 9i book: the grant the execute privilege must be done explicitly and not through a role.

Did Selftestsoftware made a mistake? Or the question did not mention or assume that the subprogram is based on invoker rights not definer right?

Quote:
Question: All users in the HR_EMP role have UPDATE privileges on the EMPLOYEE table. You create the UPDATE_EMPLOYEE procedure. HR_EMP users should only be able to update the EMPLOYEE table using this procedure. Which two statements should you execute? (Choose two.)

GRANT UPDATE ON employee TO hr_emp;
GRANT SELECT ON employee to hr_emp;
REVOKE UPDATE ON employee FROM hr_emp;
REVOKE UPDATE ON employee FROM public;
GRANT EXECUTE ON update_employee TO hr_emp;

Explanation:
The two statements you should execute are:
REVOKE UPDATE ON employee FROM hr_emp;
GRANT EXECUTE ON update_employee TO hr_emp;

Unless you are the owner of the PL/SQL construct, you must be granted the EXECUTE object privilege to run it or have the EXECUTE ANY PROCEDURE system privilege. By default, a PL/SQL procedure executes under the security domain of its owner. This means that a user can invoke the procedure without privileges on the procedures underlying objects. To allow HR_EMP users to execute the procedure, you must issue the GRANT EXECUTE ON update_employee TO hr_emp; statement. To prevent HR_EMP users from updating the EMPLOYEE table unless they are using the UPDATE_EMPLOYEE procedure, you must issue the REVOKE UPDATE ON employee FROM hr_emp;

All of the other options are incorrect because they will not meet the specified requirements.