You can use some charity to the post, of course. They almost certainly mean "never had symptoms" and likely never tested positive on a test. So, even with you

You can use some charity to the post, of course. They almost certainly mean "never had symptoms" and likely never tested positive on a test. So, even with your point that excessive testing could have shown that they had it; I think it is clear what they meant. And it is a puzzling situation.