Vita isn't massively undertracked in NA. Or at least, not by any amount worth noting (might be about 5k undetracked for last month), but I believe it's already been adjusted.
It's just not selling over there.
As for Killzone, it wasn't really "massively" undertracked either. The only thing that bothered me about that was it was obvious it hadn't sold 17k in a month, but VGC just went ahead with the figures anyway. As I've said to Brendude recently, they extract their numbers from a small amount of retailers by the look of it, which is fine. But after they've worked out all their algorithms, they need to take a step back and think "does this look correct?", rather than just sticking with the numbers no matter how silly they might seem.