I was explaining this to someone the other day: TL3 can be demoted!
So we need to think: what happens when a TL3 goes back to TL2 and gets active again and goes back to TL3? Do they get a promotion message each time they promote to TL3? 
My conclusion was: because it is difficult to know how TL3 will work for a given community, it’s better to allow Automation or a manual message from staff as the approach.