Initial results of the study suggest there is significantly impaired gas transfer from the lungs to the bloodstream in the long Covid patients despite other tests – including CT scans – coming back as normal.
It's worth remembering that there can be long term effects from any acute respiratory infection. For example is children who are hospitalised due to respiratory infections are 4 times more likely to develop asthma. Therefore 'Long Flu' is a thing, just as 'Long Covid' is a thing. The question is how much more of a thing is long Covid.