Science is about observation, measurement and experiment.
Daniel, you left out reasoning about what is observed, and reasoning used in measurement and experiment. The hypothesis about ‘multiverses’ Is falsifiable based on experiment which is what Hawking was talking about in the article.
You have every right to have a dim view of the possibility of multiverses. But your definition of science is way too limited, and inaccurate because it leaves out consciousness/reasoning. So we will have to agree to disagree.