If I don't refine the order, this test will fail: https://github.com/tangentlabs/django-oscar/blob/master/tests/integration/order/model_tests.py#L144
It'll fails because the ordering is based on date. If you get two events on the same day, they'll be on random order (and wrong order in python3 while remaining correct under python2).

However I agree it's not the right place to sort it - it should have been within the model's meta.