Wiping the hands before the face in tayammum for janabah

Question : As for the major state of impurity, if a person performs tayammum for janabah and begins by wiping his hands before wiping his face, is that permissible?

Answer : It is permissible, they say, because there is no prescribed order in janabah. However, what appears to be the case is that we should say that the order is either obligatory in both types of purification or not obligatory in both types of purification, because Allah (Glorified and Exalted is He) made tayammum a substitute for both types of purification, and the two limbs are for both types of purification. Allah knows best.