If it has a brain the size of a chimp's isnt' it rather likely that it IS a chimp or variety of chimp? And how does finding one skeletan extrapolate to an entire population or species?
I am always amused by the imaginations of some people. They find a few chipped rocks and some pieces of skeletan in Africa and create whole new classes of "hominids" that supposedly fill in the gaps of the "evolutionary chain". I classify most of this under Science Fiction and await something like real evidence.
Are big dogs smarter than small dogs?
Perhaps but it would have to be a chimp that made "miniature tools" that were found with the remains.