I think it’s important to scroll down and read the study limitations that are mentioned. It’s 1 in 5 that may be attributable to previous infection, but they also outline that this study is of course limited to people seeking care. If for every 5 prior patients who did seek follow up care, there’s 20 who didn’t and thus aren’t in the study, then it’s actually a much smaller percentage.

Post viral syndrome also isn’t unique to COVID and can be caused by influenza, mono, Ebola and other viruses, so this isn’t really unique to COVID. It’s just getting a lot of attention because so many people are impacted at the same time. (which actually has a silver lining because it means more medical professionals and people in general are realizing what long lasting impact post viral syndrome can have and looking more closely at potential solutions)