You've got a piece of the puzzle but not all of it:
By lowering the experience of just camps but also increasing how quickly they spawn it creates a penalty for failed ganks: you can't just clear and go for ganks after a full clear and be in the same place you were before the jungle changes. You have a choice:
The first camps you cleared have probable sissy respawned. Do you hard farm or give up gold and exp to try to gank, knowing you'll put that on hold to try to gank?
It's an attempt to make it less easy to keep pace with other lanes “for free” as a jungler. You can either gank less and farm more to keep up, or gank as often as you used to and, if you succeed, great, if you fail, you're behind now.