At times I see an answer in Late Answers or First Posts that is blatantly not an answer, or sometimes needs a flag of some other sort, and also turns out to be an audit. But in such cases, downvoting is expressly mentioned as an "acceptable action" for that sort of post, despite downvoting not really being semantically correct: it's not (merely) that it's a bad answer, or unclear, or whatever — it's that it's not even valid to be an answer. And having audit text that encourages reviewers to downvote (the easier option) instead of flagging seems like it will keep invalid content around longer, albeit with downvotes. (It doesn't even penalize bad answerers enough, since their answer will probably be deleted eventually, rep hit and all, so they lose rep only temporarily, and continue without the various soft or hard answer bans until that happens.)
There seems to be no existing rationale for this descriptive text, so let's see if we can hash out whether this should be shifted a bit. (Thesis: a downvote should never fail a first post audit is not directly relevant, since that's about allowing downvotes to not fail audits, while this is about encouraging downvotes to pass audits and handle posts that should be removed.)
It seems like this would be satisfied with this text:
This was only a test, designed to make sure you were paying attention. You passed. Editing or flagging as "very low quality" are both appropriate actions in this case.