See op, you're trying to logically make sense of some of the things in ME3. You really can't understate how poorly explained, structured, or written so many things are in the game.
So I'm just going to say that Harbinger, like Liara, suffered from a particularly virulent case of the terrible disease known WDD; Writer's Discretion Disease. And this particular one is caused by the ultra-deadly BioWare Strain of the Virus.
Call now at 1800-STOPWDD now to donate your time to the cure of this terrible disease, to help the life of a suffering BioWare character or plot device. These things reside in filth, and eat nothing but the worst meals, and have no hope for the future.