The Guardian headline stands in contradiction to this statement from the paper’s abstract: “We caution that a greater understanding of this effect is needed before conclusions can be drawn”.
The byline specifically says: "Exclusive: Paper by UCL professor says ‘wobbly’ space-time could instead explain expansion of universe and galactic rotation"
"Could instead explain" is not a definitive statement.
Their headline is "Controversial new theory of gravity rules out need for dark matter"
"Controversial new" tells me that this isn't settled science, nor is the Guardian trying to say otherwise. "Rules out" by itself, out of context, could imply proven science, but not within the context of the headline and byline.
