By the time there were only 4 remaining human mages out of the 12 that Matthew had killed earlier, the 4 fortunate human mages had already taken the same smoke bombs that the earlier group of human mages had used to confuse Matthew while they set up the hexagonal barrier.
Matthew had to deal with the first 7 mages with one sequence of combined movements, swinging his hands forward, pulling the aura strings to control the 4 flying aura blades, then sending one more flying aura blade out of his feet. And in that same amount of time, the 4 mages that were the furthest away from Matthew had finished their chants and threw the smoke bombs toward Matthew as fast as their hands let them.