How do you use the Success Popup in the New Form Rules?

I've been playing around with the new forms, and form rules. One cool feature is the Success Modal/Notification. However, there is no option (as far as I can tell) to have it display when a field changes.

It looks like you can display the message when a record is added or edited. So for example, if I want to display a success message when [Field A]="True!", my only option is to display message when [Field A]=True!

This means, EVERY time a user goes to edit that record, the success message shows. When would that be useful? Why would you want a success message to show every single time a user is in a record, rather than when a certain action happens (the equivalent of 'when the rule changes from false to true')?

My use case is I want a message to show when a checkbox is checked. And that's it. Just when it is checked, not every time anyone looks at the record and the checkbox happens to be checked.

Thoughts? Has anyone used the success message in any helpful way?