FPS performance - VRAM bug?

Here’s something that I find confusing: I loaded into ‘Free Flight’ and stopped at the World Map. You can see that my GPU is at 99% load, and the 3D graph shows activity. I see 100+ FPS. It stays like this for a little while, then the GPU drops to 11%, and I see 10 FPS, no 3D activity, and reported latency jumps to 100ms. Both Main Thread and GPU latency numbers remain low.

As soon as I click on the World Map again it goes back to 99% GPU, 3D activity, and 100+ FPS. This cycle will repeat.

I had exactly the same results (100+ FPS, high 3D activity, followed by 10 FPS and no 3D activity) when I first loaded into the World Map, and after 60 minutes without touching anything.

Probably a Dev Mode issue, right?