I have no idea how effective this treatment is. It is not the way erectile dysfunction would be treated in my clinical experience, let alone the use of Viagra and Cialis and the like.
There is some sort of logic to it. The reflex-stimulated muscle that closes off the flow of blood to the penis and maintains the erection is sited in the perineum. The masseur is using vibration and ultrasound to increase blood flow in the peri-anal and perineal area of the body. It may also tone up or strengthen the muscle that initiates and maintains erection, improving the reflex mechanism for erection. Finally, he uses the same instruments to increase blood flow into the penis and stimulate erection.
However, intense or prolonged vibration can numb the nerves and lower the sensations in penis under normal circumstances, thus increasing the risk of erectile dysfunction.
Whether it works or not, it may be pleasant to have such treatment from time to time.