I second that. I have a couple of spellcasters, and when I created the first one about two years ago on my current save, she was able to win a few duels yet never completed the aspiration because duels won before the prompt to win 3 duels shows up don't count.
Anyway, fast forward to present day. By now, I have eight spellcasters in my save. The first one is pretty powerful in terms of rank but not in terms of spells and potions. Her husband and two best friends are much weaker, one of her daughters and one of her sons aren't all that powerful either. I also created two new ones, both following the spellcaster aspiration. One of them is now at the point where he has to win three duels. He knows almost all spells and potions, he has the dueling feat, and he has reached the top tier, too. Yet he keeps losing to everybody, including my weaker spellcaster Sims. In fact, he lost so often he got cursed and now wants to hug random people.
Frankly, I never understood why Sims have to win duels to complete that aspiration to begin with, especially when duels are not skill- or knowledge-based but completely random.