You have correctly identified the loophole that the Off Shore scammers EXPLOIT.
Do you not yet grasp that in a Reg S placement, the company is KNOWINGLY selling stock to the "offshore scammers" you describe?
In reality, some Reg S placements are entirely legitimate. What's wrong with the exemption is that non-reporting companies don't have to tell anyone when they do one. Nor need they divulge how much stock is involved.