i think so, it makes sense when you think bout it again
Being around Athy from childhood triggered the black magic spell of him forgetting his memories of Diana and sealing his emotions to break. The black magic spell is suppose to take 6 years to fully be complete. But he met Athy after 5 years and being around her reversed the effects of the black magic.
Major events helped catalyse this.
1) meeting athy and she calling him "papa"
2) athy falling into the lake (the novel goes into more depth how that impacted him)
3) athy similarities to Diana be evident such as the lippe "flowers blooming in my mouth moment".
4) athy's lullaby
5) holding athy for the first time
6) athy near death due to mana exposure as child
As the years went by the effects of the black magic loosen the more he warmed and fully loved his daughter.
By the time of the debutante he is full on daughter-con dad that spoils her rotten.
The "curse" isn't the spell itself he used, but the cost of using black magic.
Eventually it "punishes" those who dabble with it physically and mentally.
Even in the original timeline Claude dies alone in agony because of the curse from using the spell he did. Jeanette is a catalyser to curse. Although she is "soothing" being around her will kill him quicker. Whereas, Athy is the opposite - a bitter medicine against the curse.
So.. does that mean the curse lifted up itself when Athy was young because the only way to break it is to accept her completely and regain most of his memories.