Seems to be fixed for me now. I have Max Background FPS set to 8, and after alt-tabbing out of the game the rest of my system is no longer being limited to that max FPS. I am still on the same OS build and graphics card driver, and I do not think I changed anything else related to graphics settings. Maybe fixed by something in Hotfix 1 for patch 1.1.2 deployed on August 18 (HOTFIX 1 - August 18, 2023 - 1.1.2)?