Some things that occur show up only in activity and not in reports (such as when you send troops or resources to another player, or get spied by another player). The activity list gets too cluttered and there is no kind of permanent record. If you have been attacked, you get a report and see that when you get back online, but not when you get spied or someone sends you something.
IMHO the activity list should only contain items that are current i.e. happening now, and when they are over they should become reports. This is what happens when you do the spying, but not when it is done to you. Once they become reports they should be deleted from the activity list.
You need to see incoming as activity, but not after it is over.