When I see an Answer that is code only, I believe that the Answerer created the code because they felt it was better in some way. If the Answer is better in some way, but the Answerer hasn't explained why, I feel that it is still a review, but one that I would downvote until the Answerer explains why/how their code is better than the OP.

In this case, I look at the How do I use the Low-quality posts queue? and in the section marked Basic Workflow, it says

Choose Looks OK for questions that are on-topic, sufficiently detailed and not too broad. Use this option for answers that answer the question as asked, even if they may be incorrect.

So, this is the option that I would choose, I would also comment on the answer, asking the answerer to explain the code, and Down vote the answer (when the answerer edits in the explanation, then I can change my vote)

When I see an answer that is code only, I believe that the answerer created the code because they felt it was better in some way. If the answer is better in some way, but the Answerer hasn't explained why, I feel that it is still a review, but one that I would downvote until the answerer explains why/how their code is better than the OP's.

In this case, I look at the How do I use the Low-quality posts queue? and in the section marked Basic Workflow, it says:

Choose Looks OK for questions that are on-topic, sufficiently detailed and not too broad. Use this option for answers that answer the question as asked, even if they may be incorrect.

So, this is the option that I would choose. I would also comment on the answer, asking the answerer to explain the code, and downvote the answer. When the answerer edits in the explanation, I would then change my vote.