Thanks! I think that explains enough of the issue.

Converting static types to heap ones is just one way you can use PyType_Spec. Another is writing new types, which should work much like Python classes.

So I don't think we should change the default, but rather document the use case. I'd rather update the docs after GH-9154 is merged, so this is blocked now.
 
I'll also try making an explicit `{Py_tp_dealloc, NULL}` override the inherited value, as per Serhiy's suggestion. But it'll only go to 3.8, so it won't help PySide now.