The reason these assassins didn't know the client who had ordered Andrew's death was due to another policy of the Black Wings organization. Only the job evaluators and those executing the task could know the client.
That's why, when Zaros saw the memories of the leader of the previous group of assassins, he was able to identify who had ordered the hit. Those standing before Andrew and the others did not have that mission, so they didn't know either.
Andrew didn't even need to use his Eyes of Eros to realize this, so he sighed in disappointment, and once again left without a clue of the enemy who was targeting them.
The assassins trembled in fear when they saw Andrew sigh, understanding that he now knew they didn't have the information he wanted, meaning their deaths were imminent.
