It sound like the "don't whittle toward your self you could cut yourself". This is a false statement cutting toward your own body is the safest and most controlled, this is a bit of a stretch in comparing to the axe but the basic principal applies. The same goes for the adze. In using a certain motion your body creates a break stopping the further motion of the tool.
As for the old pictures, I have always seen them as misrepresentations of the truth, this done on purpose to keep the secrets secret, allowing some truth to leak out but not all of it.