Yesterday, I had posted and my text was still in the box, so I could have clicked again. I am guessing, but that may be what happened there, double click when the text did not vanish after post.
Feb 26: That book drops for sale
Feb 27: The bulk of reviews are posted
Very recently, authors claim AMZ was throttling review posting.
Reviews do not mean purchased. If purchased on AMZ, it would say "verified purchase" by the review.