Quite surprising that the Agents didn't attack him from behind the pillar, isn't it? Well, Arsenal thought the same too.
He also thought that as soon as he got back into the fight, it would be easier for him to tell who the fake agents were. Just like the other attributes, Arsenal hoped that this would make him better than Einstein, however, that wasn't the case.
He wasn't a skilful sword fighter, but he knew a few tricks, but clashing swords with three Agent's at the same time was challenging and it didn't give him a chance to think straight.
What baffled him the most was that all three Agents felt equally real, everything in the simulation was so real. He felt every punch and every time one of the their swords cut his skin, he felt every bit of the pain, so how on earth could he tell what was real from what wasn't?