Windows in S2S operators

The text in Section 4.4 argues for not needing to define windows for streaming operators. The examples 6&7 then go and give example queries with windows. Why was the following form of query not used for Example 6?

```
SELECT ?room ?person
FROM STREAM ex:social
WHERE {
  ?person :isIn ?room
}
```

The existing proposal seems to require a lot of syntax for no benefit.
