Parenting vs. pooling

As I've been led to understand it, parenting is for images where seeing all the images is only useful to someone interested in one of the image (for example, a doujin cover parents the doujin, or an uncensored variant of a picture is childed under the censored original). And pools are for images from the same 'set' of images (so a set of 4koma or a CG set with a certain theme, or ripped CG sets from games, or etc).

But then there are things like parent:173045 and parent:174244, where seemingly stand-alone images are hidden behind some image that doesn't tell me what the hidden images are like. Why is this parented and not pooled, and what is the actual good practice for parenting and pooling?

I personally use parent/child for small variations while pools for CGs and other stuff (since it can be ordered and other things), but I'm not sure how is applied here.

I can see some cases where both are appropriate. One other reason for parenting is not flooding the front page with many variations of the same. But that's a temporary purpose.

One advantage of pools is that you can get to them any time, not just by stumbling across the image.

So I think it's a case by case thing. I can see a set of 4komas being either parented, pooled, or both. Pooled is probably best, if there's enough to justify it. Size should be taken into consideration.

It would be nice if all the people who upload doujinshis and the like would also pool them. Pooling makes it much easier to access them directly and will also make your upload more visible.