It is an expected behavior.

From https://docs.python.org/3/library/functions.html#super:

    Return a proxy object that delegates method calls to a parent or sibling class of type.

super() delegates explicit method calls. You shouldn't expect that it will delegate special methods called indirectly. For example, super() + 2 doesn't call super().__add__(2), and float(super()) doesn't call super().__float__().