This Post is reviewed by a single user and rejected by that user alone, On what criteria it happened ?
This is not a bug.
If you look at the article, it says clearly that the author is "Beebee". "Beebee" is also the person who rejected the edit per the screen shot included in the question.
AFAIK, if an author gets to review an edit and rejects it, as single review is all it takes to reject.