Differences in metrics for counting the number of completed processes per second

Hi! I use similar for my environment (Zeebe 8.6). dashboard Grafana
And relied on this json camunda/monitor/grafana/zeebe.json at a04791dd7c72c2661aecfa8490d8c6964d2cb1ba · camunda/camunda · GitHub

But when I started to load test I found a difference between the zeebe_element_instance_events_total and zeebe_executed_instances_total metrics. The first metric shows 2 times more than the second. I looked at the first metric and realized that it records the PROCESS event twice, for the parent and child processes respectively. The second metric shows only ROOT_PROCESS_INSTANCE.

Although there is another type of event CALL_ACTIVITY in the first metric. Is it a bug or is it intended to write PROCESS events to the child process as well?