Grocery store workers aren't going to be looking at aggregate statistics to make their decisions or decide how they feel. They are going to be basing it on "Joe in produce died and we think it was Coronavirus."

Then the entire store will be scared and it's not unreasonable because they probably interacted with Joe in produce at some point recently.

A lot of people aren't getting confirmation by testing. Most people will self diagnose based on symptoms. This means that official data undercounts deaths from the condition and unofficial data overcounts death from the condition, but this is a case of "which way do you bet?" And when faced with a pandemic, the way to bet is "That guy with that cough who is now dead probably died from the pandemic. No, I don't need official testing to be scared that I'm next because I pulled a shift with him recently."