I looked into these in a bit more depth. The webhooks I looked at both were ip checks that started in outage and were put in maintenance. The start of type 2 outage was reported. The maintenance did end the outage according to the API ( used a GET call on /reports/alarm/<monitorid>). And started a new outage of type 7. If the original outage period ends by putting it into maintenance it would make sense to also report that via the webhook. Preferable a single webhook message that flags a transition from type 2 to to type 7 including the transition time. That way the customer can handle that in the way that best suits them. (Ranging from ignoring it, adding a maintenance period in the receiving system, changing priority, etc).
On a side note that API call to /reports/alarm/<monitorid> adds an end_time to every outage. Including the ongoing outages (which get the current timestamp). In my view that's just plain wrong. A null value would be way more correct.