I think it depends on the type of aggregation - single host or not.
Is your aggregation over more than one host. The screenshot is a bit to small to see the real aggregation.
This is from the aggregation example and you see as this is a single host aggregation it only shows the host name on top.
I use variables to be flexible in the use of such rules so the name of the rule is a variable and as well service name which is a regex definition
Let us know.
The problem here is, is it a single host aggregation or not.
For single host aggregations the host name is only shown at the top of the aggregation as only on host is included. Now you can say i select every time that the aggregation is not a single host one but this has an performance impact in very big systems.