If Rabbi Shimon places Reuven into cherem and later Reuven passes away, the cherem doesn’t carry over to Reuven’s great-grandchildren that were never even alive when Reuven was in cherem.
It makes perfect sense if the cherem wasn’t on a specific person or people, but on anyone who conducts themselves a certain way.
Of course, l’shitoscho, cherem d’Rabeinu Gershom can’t apply nowadays. 🤔