I wonder whether Raymond Hettinger has an opinion on this PEP. A long time ago, he wrote: "freezing dicts is a can of worms and not especially useful".
https://mail.python.org/pipermail/python-dev/2006-February/0...
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https://mail.python.org/pipermail/python-dev/2006-February/0...
Not that it's entirely unwarranted, of course.