That was the old theory. The new theory is that modern humans met up with neanderthals, and apparently interbred with them, before the pure neanderthals died out.
That’s not what the article says, it says NON African humans met up with neanderthals and bred with them whereas African humans didn’t leave Africa soon enough to breed with them. There fore they are saying there is a difference between European Humans and African humans, as if they evolved at different times and in different areas.