With the beginning of Cade's left foot moving forward, and his body flowing into his attack with his light saber coming to his left. He saw how his body would move and saw how this Jedi worked during his fighting and so with light saber being on his right, it moved to his left side of the chest as the other blue blade came into contact with his purple light saber deflecting it up. The purple light saber had been positioned diagonally to the right allowing the blue blade to slide up with Cade's own momentum carrying it upwards. It didn't matter if he switch from his dominant side to attack his opponent's left side. It allowed him to safely think about his next actions as Cade was to defend himself as his next move was thought out. Then he quickly swung at the other Jedi's left side where it was open horizontally as well, leaving the possibility for defensive if the other Jedi was able to recover.