Authoritative source for the title of an article: print or online?
You appear to have found something quite bizarre: not just this article, but many of the Nature "Comment" articles appear to be titled differently in their HTML and PDF versions!

So, how to sort such a bizarre occurrence out? In my opinion, it's ambiguous whether print or online is "definitive", since many journals do not even bother with a print edition any more, and following a DOI will take you to the HTML version.

Instead, I would revert to first principles on the purpose of citation: to enable a person to find the document that is being referenced.  To this end, I suggest searching online (as somebody who might follow the citation would). Here, one finds that the HTML title predominates (perhaps unsurprisingly), and thus I would recommend using the online title in this case.