Case export has two fields that are not what they say they are
There's two fields that say "Activity Actual Date" and "Activity Scheduled Date", whose underlying fields are case_recent_activity_date and case_scheduled_activity_date. It's been that way for a while but I think it must have been a misunderstanding what they were.
It looks like they both return the same thing: recent and scheduled. I'd argue to remove the recent/scheduled completely and have a regular activity activity_date_time and call it "activity date", I guess the same way it does subject. Similarly the activity type should just be normal activity type not labelled "recent" or "actual".
I'm suggesting remove from the export instead of trying to do the same as on the case dashboard since it's a weird calculation to begin with, and obviously hasn't been available in this export forever anyway.
I believe that's what they were intended to be - the most recent activity on the case and the next scheduled activity, same as what you see on the case dashboard.