You are right absolutely right. In the thread I linked we identified two performance issues:
One regarding single digit FPS on the ground with photogrammetry on. This one can only be fixed with a full windows reinstall like you did.
Two is a performance hit due to 3D photogrammetry city objects. The symptom is similar but the FPS isn’t in the single digits. The fps is half the fps compared to photogrammetry off on the ground and it is not fixable by reinstalling windows. Basically since you fixed the first one… I was wondering if you could do a test to see if the 3D photogrammetry city objects affect your performance in any way with a specific test on the ground.
If you have time… could you test your peformance on the runway of JFK with Terrain LOD 300 or more (needs to be main thread limited) with your current setup. Then delete the 3D photogrammetry city objects from the world updates and GOTY except USA and Nordics. Restart the sim (very important) and try the same scenario again? For many of us removing those 3D cities even though they are nowhere near the USA it improves CPU performance dramatically so it would be nice to see if someone with good performance can see any changes at all.