It appears that you wandered through a wormhole on the site...just kidding.
If you check the OP's Activity here, as a 10K user you should be able to see that they asked a question on April 17th which was placed on hold by another moderator (this won't be visible to users with fewer than 10K reputation points).
Today, ten days later on the 27th (UTC time), the system (aka., "Community") deleted that question as "RemoveAbandonedClosed", as it does periodically to remove/cleanup those types of questions from the site.
As a result of removing the OP's first post, the system then automatically added their second post to the Review queue under "First Posts". Apparently it will do this any time a user's first post is deleted, even by themselves; I've seen this occur several years later.
So if you're reviewing an older post and wondering why that is, you might look at their Activity if you're a 10K user, or otherwise have an idea that their first post likely was recently removed. It's just the system's way of maintaining the quality of posts on the site, if the first post didn't go so well.