Yeah, it’s the linking of the two that don’t make any sense. Dreamer is just a trait that makes the GM have to give you cryptic clues in “dream” form. There’s no mechanics to it other than that. Dream-wise is knowing about dreams in general. Even something like Prophetic Dreams-wise wouldn’t make sense for me to be a “universal fork” as described in your first post.
This is about the only way I could see it going down:
Jane: Let’s storm the castle!
Bob: Let’s wait, and I’ll see what my dreams tell me…
<Bob tests Prophetic Dreams-wise vs at least Ob 4 as a linked test>
Note that linked tests in BW have failure consequences like any test, the +1 Ob is in addition to that. So for things like this I twist pretty heavily on failures.
Full disclosure: I don’t like the Dreamer trait much, or “universal fork” abilities.