A further possible complication is that any given "tidying up" session might involve renaming an Album or Photo(s) or deleting an Album or Photos, or moving a Photo; that list is not exhaustive. It might easily not fit into a single Notification /however/ long the aggregation time was.
That's an interesting point. For that use case the aggregation (or exclusion) would be better focused on the user than the activity.
I'm not sure how difficult it would be to detect that automatically, but given that the first event kicks off a timer it might be possible for the software to look for a sequence by the same user as well as a sequence of the same event. Maybe only if the user is a mod/owner, but maybe not.
It has the potential to be complicated...
Too true. Sometimes simple to implement is not simple to use, and vice versa. Great things happen when you find a concept that makes the two align.