Lower FPS On The Ground?

Many posts have described lower FPS on the ground compared to in the air. Occasionally I’ll taxi very close to a wall so no other scenery or ground objects are visible. Since there are no screen updates, I would expect 100+ FPS. There is nothing changing. However, the FPS drops to 10-15 FPS.

I’m wondering if MSFS has X-ray vision and it is not only rendering the wall but everything including ground aircraft and vehicles behind it going out miles away. I have no idea why it would do this. Just another MSFS mystery.

I’ve noticed this too, and especially when I get a sudden pause as soon as the wheels touch the runway on landing. I wonder if the sim struggles to calculate handling and physics during taxiing?