Actual study: https://www.nature.com/articles/s43587-024-00692-2
We collected longitudinal biological samples from 108 participants over several years, with a median tracking period of 1.7 years and a maximum period of 6.8 years, and conducted multi-omics profiling on the samples.
That's not a lot of people studied for not a lot of time. It feels like the wording in the Guardian article is trying to misrepresent things.