Last August, James Knight posted to python-dev, "There's a fair number of classes that claim they are defined in __builtin__, but do not actually appear there". There was a discussion and James submitted this patch:
I'm -1 on adding these to __builtin__. They are just distractors and have almost no use in real Python programs. Worse, if you do use them, then you are likely to be programming badly -- we don't want to encourage that.
Also, I take some of these, such as dictproxy and cell, to be implementation details that are subject to change. Adding them to __builtin__ would unnecessarily immortalize them.
The final result of the discussion is unclear. Guido declared himself +0.5 on the concept, but nobody has reviewed the patch in detail yet.
Even if Guido were suffering from time machine induced hallucinations that day, he still knew better than to go a full +1.