Isn't this article about correlation?
Isn't the point of the article that something about eating less meat (whether it's lifestyle, actual dietary effects, or something innocuous) correlates, whether or not there is a causal relationship*, to significantly increased longevity?
If there is no direct causal link then all correlation does is suggest such a link. You have to FIND the link and prove its real in order to make this about something.
X is observed in people doing Y is not a scientific breakthrough, it is an observation. If not all people that do Y have X there is no story, just more work to get to the bottom of what is going on.