If it’s any solace, type checkers don’t recognise old style iterables as compatible with iterable. And in all the years of mypy, this missing support has only come up a couple time, especially so once people mostly stopped using Python 2.
I’m aware of one popular library (torch.utils.data.Dataset) that relies on old style iteration for providing iterability. I tried to get them to use __iter__, but they claimed some users had use cases where it wasn’t actually an iterable. Of course, most code assumes that it is iterable (including plenty of code in torch), so I wasn’t sympathetic to that concern. But I didn’t feel like arguing the point 