Interactions in Canvas are included in reports "when you contact the student via Conversations or when you leave a comment on an assignment." [source; I'm pretty sure Conversations means Inbox in this case].
Comments on rubrics to students as well as replies by instructors to students' discussion posts should be included in these "Interactions" analytics. That way you can get an overview of how often you've been touching base with students in these two other categories. Where both categories are concerned, you'd be able to ensure you're spreading your attention/feedback widely across your class.