The problem is that such a "weights and heights" measure is an extremely simplistic measure. Just because there are modern humans who are midgets, that doesn't mean that an Australopithecus would be taken for a "normal" modern human if one were to be brought to the present using a time machine. You'd still freak out if you saw one walk into the 7-11.
I don't know *any* modern humans who look even remotely like *this*:
Massive brow ridge, *NO* forehead, a braincase you could wrap your hand around like a football, a prominent protruding muzzle, small close-set eyes, jawbone larger than the braincase, etc. etc. Compare to the proportions and angles of a modern human skull:
