Generator input is unordered

Elastic Stack Logstash
1

According to this documentation and logic in general I assume this input should process specified lines one by one in the specified order, not random or anything else.

But it it's output is in random order.

Also the text from the above link contain a mistake. It should be:
"The above will emit line 1 then line 2 then line **3** , then line 1 , etc…"

2

Once the filter section gets hold of the data it is possible that it will be processed in parallel by multiple threads, so at that point ordering is no longer guaranteed.

3

Even if there is no filter section? I have only input with generator and output with stdout