I would not recommend making any firm conclusions or recommendations based on short term results of six divers. I would especially refrain from using terms like "the damage to the lungs is irreversible" when they have only had a few weeks of follow-up.
Apparently, from what I can gleam from the English translation, two divers had exercise induced hypoxemia while two others had exercise induced reactive airway disease. They say four STILL had significant changes on CT scanning implying that they were sick enough at one time, though apparently not hospitalized, that a physician had ordered a previous CT scan. Finally, any conclusions regarding the effects of increased partial pressures of oxygen in divers who have suffered COVID-19 is purely speculative.
I would recommend taking the above information with a "grain of salt" for now while awaiting further data. It is definitely interesting and is thought provoking. We just need to wait for larger, more controlled studies with longer follow up before becoming overly concerned.
If a diver had a mild case of COVID-19 and is now back to jogging 5 miles per day without issues, they can probably return to diving without restrictions or further testing. However, if a diver had a prolonged ICU stay from the infection, especially if they required intubation, maybe they should have follow up CT scans showing resolution of the changes and maybe even pulmonary function testing prior to resuming diving. Only time -- and, more importantly, DATA will tell. The Belgian Hyperbaric Medical Society has released some recommendations which are similar to what I stated above. Hopefully, organizations like UHMS and SPUMS will provide some guidance as well.
As DDM mentioned above, the best advice at the moment is for any diver who has had a symptomatic case of of COVID-19 to be examined by a physician with diving knowledge prior to resuming diving.