Hi @Clark_Munson, welcome to the Asana Community Forum and thanks for taking the time to share this feedback with us!
As it stands, rules only apply to subtasks that are added to the project: How to Use Asana subtasks | Product guide • Asana Product Guide. If you associate the subtasks to the the project, all rules will also apply to subtasks and you can receive notifications in Slack.
We already have two threads on this topics, I recommend you to upvote here:
I hope this helps! 