When starting Windows Standalone in a -batch mode it eats around 60% of my Core i7 CPU (it is empty project with empty scene !!! )
Note: when I run this Standalone without -batchmode flag - it uses 1-2 % of CPU

Tested on Windows 7 64b - happens in all versions since 5.6.3.f1(didn't check earlier versions)

For more info on -batchmode flag please read this docs page - https://docs.unity3d.com/Manual/CommandLineArguments.html

How we can reproduce it using the example you attached
To reproduce this from new project:
- Create new Unity project
- Go to File->Build Settings and build Standalone
or simply
1 Download attached folder
2 Find "testBatchmodeBug.exe" file and run it in comand line with -batchmode argument
or simply run "testBatchmodeBug.exe - Shortcut" shortcut (it already has -batchmode argument applied)
3 Open "Windows Task Manager" and find "testBatchmodeBug.exe" process in "Processes" tab

Actual results:
it uses up to 60% of my Core i7 CPU - please see attached image

Expected result:
this Standalone should use 1-3 % or so of CPU

Workaround: set Application.targetFrameRate to desired frame rate and disable VSync