Siddhi delayed query

I am struggling to understand this query:

from heartbeats#window.time(1 hour) insert expired events into delayedStream;

from every e = heartbeats -> e2 = heartbeats[deviceId == e.deviceId]
  or expired = delayedStream[deviceId == e.deviceId]
within 1 hour 10 minutes 
select e.deviceId, e2.deviceId as id2, expired.deviceId as id3
insert into tmpStream;

• The first query delays all Events by 1 hour.
• The second query filters all Events that occured 1 hour ago and no newer Events have been found.

This works but I dont understand this part:

from every e = heartbeats -> e2 = heartbeats[deviceId == e.deviceId] or expired = delayedStream[deviceId == e.deviceId]

The second part of the query (or expired = ...) checks if the Event with the given deviceId is on the delayedStream. What is the purpose of the first part and how does it come together, that this query finds devices that sent no data for more than 1 hour?

I don't think the above query will be accurate if you want to check if a sensor did not send reading for the last 1 hour. I tweaked the windows as 1 minute and sent 2 events,

[2019-07-19 16:48:23,774] heartbeats : Event{timestamp=1563535103772, data=[1], isExpired=false}
[2019-07-19 16:48:24,696] tmpStream : Event{timestamp=1563535104694, data=[1, 1, null], isExpired=false}
[2019-07-19 16:48:24,697] heartbeats : Event{timestamp=1563535104694, data=[1], isExpired=false}
[2019-07-19 16:49:23,774] tmpStream : Event{timestamp=1563535163772, data=[1, null, 1], isExpired=false}

Let's say events arrive at 10 and 10.15, the outputs at the tmpStream will be at 10.15 (first part) and 11 (due to delayed stream). The second match is incorrect as it has to match at 11.15 as per use case.

However, if you want to improve the query you can use the Siddhi detecting non-occurance pattern feature for your use case, https://siddhi.io/en/v5.0/docs/query-guide/#detecting-non-occurring-events, it will be simpler