How to reproduce:
1. Open the Task Manager
2. Create and open a new 2D Core (Built-in Render Pipeline) project
3. Enable the “Run In Background“ checkbox
4. Sset the Fullscreen mode to “Maximized window“ in Project Settings > Player > Resolution and Presentation > Resolution
5. Build the empty project
6. Make the Player windowed (if it is not yet) and bring the Player to the foreground
7. Observe the Task Manager
8. Minimize the Player and observe the Task Manager again

Expected result: GPU usage of the Player is around the same if not less than before minimizing
Actual result: GPU usage doubles at least

Reproducible in: 2021.3.45f1, 2022.3.51f1, 6000.0.24f1

Reproduced on: Windows 11 Pro (23H2), Windows 10 (by the reporter)
Not reproduced on: No other environment tested

Note: While testing locally, GPU usage is ~5% when running in the foreground, and 8-15% when in the background