I think it's a little hard to use it as a touchstone, since so many individual services (school notification, weather notification, emergency notifications) use text alerts.

But if you're asking whether drills use an extra "drill only" set of messages, that would be a good question.

Would kind of defeat the purpose of the drill, though; the purpose of the drill is to test the system as-is.

So if you go to documents showing preparation for a regional emergency drill, for example, they might talk about using "the regional emergency notification system" during the drill. But that's because in a real situation, this system would be used.

But maybe you're asking whether in a drill text messages would be marked in some way, i.e. "THIS IS A DRILL" after each text? I would think that would be likely.