They are probably very specific search terms that are repeated in the documents and might be unique enough to show up in any documents created by someone plagia

They are probably very specific search terms that are repeated in the documents and might be unique enough to show up in any documents created by someone plagiarizing the Waymo docs. The fact that 31,000 other documents also contain these phrases but are "not substantive" makes it seem like the search terms are somewhat generic but definitely appear in the Waymo docs. Uber might have ruled out all of those other docs by just looking at the dates the docs were last modified. If they are older than when Levandowski or any of the other people previously employed by Waymo joined Uber, then they can probably be vetted as original IP.