Yeah, that portion of the doc kinda surprised me as well. Culling at that level doesn’t strike me as very useful because of that.
For completeness, culling can also be configured within a Notebook server. In this case, the target of the culling operation is the kernel itself. In addition, there are more options - like culling connected kernels (probably what you’re after), or culling busy kernels (which I wouldn’t advise). See the options on MappingKernelManager. Since I believe you’re focusing primarily on resource consumption this may help, although I suspect the issue is the Notebook server itself. You need it to go away.
PS. Your links in your original post should be edited to not include the trailing colon.