I agree, but that is not what the study in the linked article shows. It looks like they only looked at people who had previously tested positive for COVID:

> They ran an analysis of the first 509 COVID patients treated at Northwestern Memorial Hospital and, in a paper published later that year, reported that 42 percent of them experienced neurological symptoms upon contracting COVID, 63 percent upon being hospitalized, and 82 percent over the entire course of the disease.

From what I have seen, this is the same with the other long COVID studies I have seen as well as the other references in this article. Do you have an example of a study that compares long COVID symptoms of people who tested positive compared to people who never had COVID? I would be very interested in reading that.