What I meant was isolating all the encounters to a specific type, which makes it easier to hunt a specific target. Of course, there won't always be just one Pokemon, there could be multiple of the same type, but still makes hunting a certain mon easier. I understand what you mean with the group thing, but I was providing a more general explanation.
With Applin, I know it's the only dragon in the forest, but since it only spawns in trees, it can be hard to see, so the afk method seems more efficient since you can stay in one place and there's no chance you will miss a shiny.