The point #3 was referring to the new requirement for an atexit handler in order to not only kill the processes but to also wait for them at interpreter shutdown. The sub-processes (and associated resources) in the example are definitely freed as the parent process is terminating.

The recommended handler is not even always desirable (spawning daemon processes, key agents), it increases the code verbosity, impacts performance, and can even cause problems as child processes cannot always be waited on reliably (python 2 but also child -D state and platform-specific restrictions).

I suggest to disable such warnings during interpreter shutdown.