This is a meta review that looked at a selection of other reviews that all suggested a correlation does exist. This meta review is pointing out that they believe there's not strong enough evidence in those other reviews to say concretely, scientifically, that there's a link. Only a tentative link. This is in no way a study saying that there is no link. It's a study saying there's not enough of a preponderance of evidence in all these other studies to definitively say there's a link.