Hm, I don't see any mention of post_scaledown_task in there - can you find the log that mentions that? If the scaledown succeeded, then that task should be mentioned in the log, and it's the post_scaledown_task that does the service removal.
The log makes it look like the post_scaledown_task succeeded. Can I see your environment? How long did you wait before checking whether the service was deleted?
Created attachment 1230735 [details] scale down attempt log