> Is there any sense in accepting non-types as the first argument of issubclass()?

No, though it is not (clearly) documented. The docs mention TypeError, but only for the second argument if my reading is correct.

In practice, issubclass() raises a TypeError if the first argument is not a class object:

>>> issubclass(1, int)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: issubclass() arg 1 must be a class

Though, as I mentioned above, behavior for ABCs was always weird.