Either way, what is most interesting, Nielsen says, is that the results show that mating with other groups was an important source of beneficial genes in human evolution. “Modern humans didn’t wait for new mutations to adapt to a new environment,” he says. “They could pick up adaptive traits by interbreeding.”
I have a bit of issue with the notion of the source as "important". Useful perhaps. Maybe even "potentially important". The thing is that we don't know whether the alleged interbreeding produced many other variations that were undesirable - with high mortality rates so that they failed to survive multiple generations. It could even be that most of the offspring were still-born or sterile. That doesn't take away from it being an interesting conjecture to explain an unusual variation.