18.06 is risky. 18.06, in any point version, does not have different images for Micron and Hynix variants. Complete support for 3370 came along just after 18.06 has been tagged, and has not been backported because reasons. I would recommend 19.07 (and probably hold out just a bit longer for a the release) or a current snapshot.
True, the article is super bare-bones and could use some updating/pruning. But to its credit, it links to the commit message which is actually rather detailed and explains the two variants (again, since snapshots of last year, or 19.07).