The ADT system is a completely separate system using a different network protocol which does have exit delay. See the existing active thread for more details:
The new ADT system has a smart things hub inside of it which you can use for home automation, but you can’t use your existing smartthing sensors with the security part and it’s not clear yet if you can use the special security sensors with the SmartThings part.
Again, see the other thread for more details.