Their idea seems to be that using a short term intervention acts on the prebiotic effects and improves the gut microbiome, as compared to a lower dose over longer time. It does make sense.

It study design would be more interesting if they had a branch for "overnight oats".

Pro tip: just pour boiling water over a bowl of rolled oats and let them soak for a few minutes.

*in a study looking at people with metabolic syndrome who consumed a calorie-restricted diet which included two days of eating almost nothing but oatmeal.