I would submit that this is huge for Vector as a character. As has been pointed out by others, most (if not all) of the Agent’s companions are untrustworthy. SCORPIO tries to kill you multiple times. Lokin blackmails you into taking him on, has a lifetime of secrets and is spying on everyone else. Raina is delightful, committed to the Empire, but she still has her own secrets and she ultimately does terrifying things to keep them. Kaliyo is... Kaliyo. People think they can trust Vector. From what i can tell, most of them feel this way because he is amiable, loyal and surprisingly humane for an imperial character. This is despite the fact that he’s been chemically conditioned to be part of a society that is not only foreign but completely alien in its philosophy. But in this moment, in the final moments of the IA’s Alderaan story, he chooses to side with you and the Empire. Even though that burns the hell out of him.  This is great storytelling and characterization. They are SHOWING us, rather than telling us, what is most important to the character.