Going to stick my neck out and say that its wrong.
Yes the stream aggregate gets called first... but it hasnt finished. So is the important part which gets called first or which gets finished first? Personally i think its the part that gets finished first thats important (or more precisly the thing that performs its purpose first). I cant say a function has been executed when it hasnt actually done anything.
Could be a language thing though that i put a different meaning into "executes" then everyone else 🙂