Yes, "ground glass opacities" are often seen during and after bouts of pneumonia and other lung illnesses. Sometimes they disappear as the infection subsides, other times it takes a while. Or if the infection or illness becomes chronic the GGO may stay.
When I had MAC and Pseudomonas at the same time, my lungs were full of GGO plus nodules, possible cavities... ow 5 years later, I still have Bronchiectasis, a few small nodules and some scar tissue. No GGO on the last CT 9 months ago.
So all of these signs can come and go.
Sue

This is a good discussion. I have all these CT abnormalities and my new pulmonologist explained their significance. Dx is bronchiectasis and probable MAC relapse. Waiting for cultures. Smear was positive.

I knew I had seen this explanation before, but I just had time to look for it this morning:
"Ground glass opacity (GGO) refers to the hazy gray areas that can show up in CT scans or X-rays of the lungs. These areas show increased density inside the lungs that could indicate pneumonia and other respiratory disorders.
The term comes from a technique in glassmaking during which the surface of the glass is blasted by sand. This technique gives the glass a hazy white or frosted appearance." From:
https://www.medicalnewstoday.com/articles/ground-glass-opacity

So, in essence, the CT findings are saying to the doctor "Consider this along with your patient's health history and other symptoms."
By the way, if you do Google for a term, and "Med News Today" comes up as a source, their explanations are usually very clear, balanced and understandable. MUCH better than any Facebook page or blog, and much easier to read than a research paper from NIH.

I like to find these explanations in layman's terms so I done' need a medical encyclopedia to figure out what the report is saying!
Sue