Hugh Kimura, writing about the new Spotlight search suggestions for App Store apps in iOS 8:

At this point, there doesn’t seem to be a way to optimize for Spotlight Search. Even searches for the most popular app names and keywords return inconsistent results.

It does help some well established apps. But we need to wait for Apple to refine the algorithm, in order for it to benefit more apps.

With ASO now being an important factor for developers to consider to properly market their apps, it’ll be interesting to see if and how search in Spotlight will evolve. I’m finding it to be much faster and intuitive than App Store search, but its results aren’t consistent.