Because in the ending of Halo Reach, Noble 6 took off his helmet and take the last breath between the Elites, then they block the view of the Spartan’s action. I don’t know He’s dead, taken hostage, or bring him alive to join them? If Noble 6 survived from the fleet or escape the planet reach, then he’s the Agent Locke.
Locke’s backstory
> Born on the colony of Jericho VII, Locke was orphaned when the Covenant invaded his homeworld in 2535, being evacuated from the planet only minutes before its glassing by the Covenant. Losing everyone he had known, Locke was placed in a state orphanage with other children who had suffered a similar fate. Upon growing older many of his compatriots enlisted in the UNSC, eager for revenge against the Covenant. However, Locke continued to blame the government for their failure to defend his homeworld and came to the conclusion that the UNSC was incapable of protecting its citizens. As a result, he became a freelance tracker and assassin. Locke’s atypical behavior and questionable allegiances eventually caught the eye of the Office of Naval Intelligence, who planned to train Locke into a specific role within their organization. Seeking a greater purpose in life, Locke accepted ONI’s offer to join and entered their extensive training program where he honed his skills to perfection and became one of ONI’s top field operatives.
straight answer… No.
Locke became a Spartan after 2552, secondly noble 6 is dead and acknowledged as being so in new blood by Jun and buck.