This isn’t solving per se. In this particular case, all three cubes are in the same simple configuration (with slight cube rotation before the predefined “scramble” so they appear different). The juggler simply memorized the short solution to this particular simple configuration. This is why he is able to “solve” the three cubes in 18 seconds. I definitely doubt that he can do this with three cubes scrambled by a third party.
If you want to see a real cuber juggling and truthfully solving three different (real) scrambles, see Ravi Fernando. He has done this in front of many real cubers so there is no doubt about his achievement.
