Edit: ok re-reading the article it says supermarkets were the most common place visited before testing positive, but then PHE states this is no proof that is where it's contacted.
In fact, it's almost guaranteed to not be the place where you contracted it.
I suspect that the issue is that people are going "Oh, I need a Covid test. If it's positive, I'm going to have to semi-quarantine. Let's stop at the grocery store before getting the test."
I think two things are being confounded here: (1) places most likely to contain people with COVID; and (2) places most likely enable COVID to infect someone.
Many people go to supermarkets; they’re like central hubs in a network. It doesn’t mean that as much transmission happen there as in smaller confined places like houses and bars.
You are probably conflating risk of infection per person with total number of persons at risk. It can be true that churches and bars are more risky for those that visit them, while more people get infected at groceries and big-box stores just by dint of high volume at lower risk.
Just anecdotally this matches something the mayor of El Paso said a week ago - 33% of their cases were "big-box", followed by bars and restaurants, then "everything else".
Cite, please. This matches nothing I have seen.
The biggest vectors seem to be Number 1: churches and Number 2: bars/restaurants.