Regarding the study this is a both can be true situation. There can be (1) a population who is disproportionate in their beef eating, and (2) a study about 12% doing the most on any given day can count in favor of that group being real and (3) not everyone from the daily 12% is part of the DBE group. It's more likely a venn diagram overlap, and where it doesn't overlap, people who aren't part of the DBE are incidentally in that 12% while being closer to average in the aggregate over the longer term. Those facts can all sit together comfortably without amounting to a contradiction.
By saying “on any given day” you are suggesting it’s a different 12%. The article does confuse this by identifying cohorts that eat more beef. But it’s a tautological label based on the survey data. They identify some correlates, like being a 50 something male. But there are males who are 50 something that don’t eat any beef. They’re not included in the 12%.
The 12% is just the outcome of the sample. It doesn’t mean they’re a consistent cohort.
Example:
* on any given day x million women give birth
* there are x million women who give birth every day
Like, it’s probably something closer to 40% than 12%.