I seriously doubt that the dramatically increased exposure you get as a grocery store worker makes you safer, and suspect this effect reverses once you control for risk factors.
Working in a grocery store rather than staying at home is, intuitively, less safe. If they're not able to carefully control for the risk factors, they're doing a disservice to report that figure by itself. And it's a non-trivial amount of work to do so such controls, simply to appease those who repeat over-clever contrarian factoids like that one.