It doesn’t make sense because Ivankov says
weakness , Sanji’s weakness in One Piece has always been Woman. We’ve known that since Alabasta. Sanji’s weakness for woman has even effected his Haki at some points.
But now we got Gaban with this Masochistic Instability thing, but that’s not something you can identify in a short period of time of knowing someone, only Zeff and The Strawhats would be able to identify that in Sanji. There hasn’t been a circumstance in Elbaf for Sanji to show that he has this issue. Unless a Strawhat told Gaban about Sanji. Like Luffy telling Gaban about Sanji’s nature.