About Question enthuware.ocpjp.ii.v11.2.1738 :

[webber]

It should not be in "parallel streams" section.

[admin]

Ok, so now I know the reason why they are categorized into that section. In official exam objectives, the "Parallel Stream" topic has two subtopics and one of the subtopics is - "Implement decomposition and reduction with streams". This and the other two questions that you reported belong to this subtopic and that is why they are showing up under "Parallel Streams" section.