Wrong way round. Your RM head can do 4 ohms minimum load, which means you could run two 8 ohm cabs or one 4 ohm.
They do this again because of this common myth that “getting full power from my head” means more volume. Which goes back to Bill’s post I shared earlier
Two 8 ohm 4x10s will be louder than one 4 ohm because you’re moving double the amount of air, not because you’re running the amp at its nominal minimum impedance.