Title says it all but I need to add at least 30 characters.
That would be my fault. Late answers are only enqueued if the author has no more than a certain reputation level. Today, I raised that limit from 10 to 50. My intention was to add a minimal number of reviews. But I didn't account for the backlog of late answers that would be added to each and every site on the network. (Truthfully, I misread the code.)
Now that those answers have been added to the queue, I'm not so sure it was a bad idea. After all, this queue is designed to surface potentially hidden gems. Each review task can be cleared be a single person voting, commenting, editing, flagging or even upvoting an existing comment. So far the queue on other sites has shrunk rapidly as a result. As an added benefit, this is a rare opportunity to make significant progress on the Late Answer Reviewer badge if you are into that sort of thing.