I mainly agree on closing this issue as we already have a warning about this behaviour in gc.get_referrers and other friends.
On the other hand I am still a bit afraid of a crash that could happen if the GC does a pass and one of these tuples is in an inconsistent state. Is possible that this crashes Python without the user calling ever any function from the GC module. I need to do some investigation around this, but I agree that this is a separate issue, so I will open a new one if it happens to be relevant.