However, if this is important to you then you want Signal to stop telling Android to make the notifications. If it doesn't exist nobody will accidentally make it available.

Deleting that history is good to know about after the fact, but preferably lets just not create the problem.

I need the notifications though.

But you can set them without content. That actually works with signal because all it sends through Google Firebase is a notification to wake up the app. If you have the content turned on the app basically fills the content in the notification locally. But you can turn that off.