In this case the problem is that the score of the post is too high for being deleted in this form. The idea is that apparently there are some that find value in the contribution and so it maybe should be kept after all. The score at the end of the review is not predictable in advance.
In any case, the exercises was not pointless. It is now a "disputed LQ review" and this raises an auto-flag for moderators. Thus eventually one of us will decide the fate of the post. Likely it should be transformed into a comment and I will do this soon (although it is redundant as somebody helpfully posted the information already as a comment).
Another thing that can happen is that the author undeletes, which they can do if the post is delete in this form. But again it raises the above mentioned auto-flag.