When I build in 6000.1.0a9 2DURP template with default settings I see 35%+ CPU usage. But, if I grab the window and move the build around it drops drastically while still running as normal. As long as I’m holding the mouse down on app bar it drops back to 2-4% as expected.
Let me know if you need any additional information.

No. Because we don’t use Task Manager to assess application performance or behaviour. It is highly inaccurate / misleading. The effect you see could as well be OS behaviour throttling the Window content updates.
Use Unity Profiler to analyze your game’s performance. If you can replicate the behaviour in the Profiler, please report a bug.
It’s a completely different behavior for the same cloned game between 2022 and 6000. 6000+ is rapidly overheating my computer while 2022 doesn’t.
Unity 6000.1 - Holding the mouse down on the window it produces high CPU in profiler and low CPU in windows while cooling the PC down and the cooling fans goes silent.
Unity 6000.1 - Not holding the mouse down on the window it produces low CPU in profiler and high CPU in windows while the PC begins to rapidly overheat and the fans run at max.
2022.3 - Low CPU and not overheating and game runs as expected regardless of focused or not.
Two compared. Memory usage is also nearly double between the two versions.
Found another post on the discussions forum from a few days ago about mobile devices running very high CPU with a nearly empty scene in Unity 6. Why is CPU and GPU usage so high on almost empty scene
First thing I would check is how many FPS the builds are running at. My first guess from your symptoms would be that VSync is disabled.