"Ella ha roto con él pero ________ así él sigue insistiendo.
She broke up with him but even so he keeps trying.
(HINT: aún or aun?)"
I've already forgotten which I picked, but I got it wrong. My confusion is that according to the lesson, both "aun así" and "aún así" mean "despite that". I can't think of a sentence in English where "even so" is not interchangeable with "despite that". It certainly seems like they are interchangeable in the quiz question above. Is there a nuance that I'm not grasping that explains why only one of the options is correct?