As a historical note, the docs are probably correct...but at some point relatively recently we fixed the inconsistency in what was raised in the thread and threading modules, but obviously no one noticed that multiprocessing had the same issue.  It could be that a comment should be added to the thread/threading code mentioning the multiprocessing clones, and vice versa.  Or perhaps the code can be unified?  I suspect the clones exist primarily because multiprocessing was originally an external project.