According to Grace Note's answer on meta.SE, answers are put into the late-answer review queue when the following conditions are satisfied
- the answer was posted at least 30 days after the question was asked, and
- the answer was posted by a user who has 10 or less reputation (disregarding suspension).
In particular, it does not check the reputation of the user at the time of posting nor how old the answer is, so that a user with, say, 11 reputation can post an answer to a two-and-a-half year old question, have no reputation changes for a couple years, receive a downvote dropping them to 9 reputation, and then have their years old answer put into the queue.