The 20%-30% is likely only associated with those who end up on a respirator with ARDS or severe pneumonia, and is caused by pulmonary fibrosis. For others, the amount of damage is likely proportional to the severity of the infection in their lungs. The mildest cases might result in no damage, getting worse as your lungs are more effected. Still, even a 5%-10% loss that only really bothers you when you're hiking, skiing, biking, working out, etc sucks. BTW, I commented on this a month ago, after I found similar information about long term outcomes in SARS/ARDS victims. In a significant portion, the cardio-pulmonary damage resulted in Chronic Fatigue Syndrome and depression.
The story posted yesterday was very vague and studies from SARS-COV victims can't directly be applied to SARS-COV2, but it's pretty clear there is going to be some correlation, and some survivors are going to suffer long term cardio-pulmonary damage. The long term damage SARS-COV2 causes probably won't be quantified until next year.
That brings up a question.
I wonder how many of those succumbing had other previous infections that had already compromised their lungs.