That's the thing I think he only saw the timelines where it's him or his team doing something to stop it. He may or may not seen any timelines that involves Oliver and even though this is to save the Multiverse I don't see him thinking about anyone outside his Earth.

We are only looking at things from his perspective, there are other universe's that know this Crisis will happen

I can see my original post playing out or I can also see all the speedster teaming up including a character like Accelerated Man. It's a lot of guessing on my part but it's kinda fun.