I'm going to close this issue because it's not a bug.

I understand your question now, as well as the source of your confusion: you thought that traceback is "the thing that is printed to the screen when an exception is raised" and that __traceback__ is something that controls how it's printed.  Those are two misunderstandings and I can see why you thought, on that basis, that there is a bug.

The traceback is only part of what is printed to the screen when an exception is raised, and the __traceback__ field of an exception is a pointer to the actual traceback data.