When Diane and I got our Class B CDLs in Minnesota, we were required to both pass the air brake written test and take the road test in an air-brake-equipped vehcile to receive the air-brakes endorsement. With no air-brake-equipped truck to road test with, we would not have been able to demonstrate air-brake knowledge when we did the pre-trip inspection as the examiner watched and questioned us.
We did not try to rent an air-brake-equipped truck from Penske, but the rental company we did call refused to rent us one since we did not then have CDLs with air-brake endorsements. For our road test, we rented an air-brake-equipped truck from a company that provides them at the test location for that purpose.