Those are each reasonable things to say with certain conditions and caveats. I would guess the issue is with various experts and policy makers trying to simplif

Those are each reasonable things to say with certain conditions and caveats. I would guess the issue is with various experts and policy makers trying to simplify things "for" regular people. Different people have different priorities and different summaries. Another issue is that some health officials won't recommend something until there has been an official study result. For example, it was very likely that mixing vaccine types would result in stronger immune responses. But almost no one was willing to recommend it until there was a study done. That's why Britain finally put together a tiny quick study just to get a result out that they could point to. A related issue there is that the recommendations are all based on the quickest results to study. The short 3-4 week spacing was recommended only because testing longer gaps takes longer.