Great use of metaphor to make a complex and subtle technical concept into a readily-understood one-liner.
Herding was mostly done by people, often kids, and fences, though some neighbors did use herding dogs.
I can understand how trained herding dogs can also be important, but it was certainly not my experience in the countryside.
Oh, I didn't realize it was in widespread use. But still. Someone thought of it, and it's great use of language.