Image should be able to explain it:
Bug? You mean feature?
I personally can’t find a use for this, but I’m sure this could actually be useful for some person.
I don’t know what you expect? They can’t very well start the full fog at infinite range, so instead it makes it act as though it’s 0.
Edit: It could disable fog altogether, but perhaps that isn’t a feature of fog and it only takes absolute values.
“Doctor, it hurts when I do this”