No, you’re getting confused. An email list management system has far different data than the system that dispatched the fucked up template to it. Additionally, whether or not someone is an active subscriber no impact on them being in the mail system in general.

The whole point is that the piece that screwed up and pushed this template would have no PII access itself.

Beyond it being PII, it’s just how you sanely design these types of mass email/sms/push notification distribution system.