When Amon used his commands to position his people, he always had four people near the exit. He placed them there to prepare for what was happening now, which was when Lu Zu decided to bail.
The four were surprised when Lu Zu rushed at them. They knew how fearsome Lu Zu was. They saw many of their comrades die in that man's hands. They were about to move aside when Amon yelled not to let Lu Zu escape. This caused them to pause.
Rather than staying in position because of obedience, they stayed mostly because they were startled by Amon's yelling. They were used to following his command, so there was a second when they were undecided between compliance or survival. When their brain finally decided on survival, it was too late. Lu Zu was already upon them.
