The headline might be what you expect, but the article contains mathematical details about the relationship between antibody levels from the vaccines and neutralization. It also models antibody levels over time to see what immune protection we'll have in the future. Did we know the expected efficacy of the vaccine against severe Covid 750 days post-vaccine before?
But not everything turns out as you'd expect, so it's important to actually test and provide evidence.
Yeah, it just seems unusual for Nature to publish such a confirmatory outcome.