I answered a question ~380 days old and both my answer and the question have a positive score. Requirements were met a few hours ago.
The requirements for Backlog:
Answer a question from 2019 or earlier that does not have any answers. Both question and answer must have a positive score.
While a question could have a deleted answer, that I cannot see due to < 10k reputation, which prevents this hat from being awarded as it is currently coded, in no practical way is a deleted answer an answer... See this accepted answer on how the Enlightened badge is awarded for a similar situation.
Here is the question: How to refresh a blazor sub/child component within a main/parent component?.