Yes, in bug2.py we have different cycle.

a ↔ b
↓   ↓
v → d

a and b are in a cycle, and therefore v and d are in cycle. I think that in such case v always should be destroyed before d, independently of a cycle that refers them. And this is the same situation, as for io classes. A TextIOWrapper object refers a BufferedWriter object, a BufferedWriter object refers a FileIO object. and some cycle refers a TextIOWrapper object. As a result a FileIO object can be closed before a TextIOWrapper object or a BufferedWriter object flush its buffer.