Or the long term symptoms are mostly nocebos, and/or the only reason they are regarded as having one cause instead of many (as well as symptoms they would have

Or the long term symptoms are mostly nocebos, and/or the only reason they are regarded as having one cause instead of many (as well as symptoms they would have gotten anyway) is that the person in question knows about "long COVID", or a combination of those and possibly even something that's really causally related.