Interesting study. I think there is no "one size fits all" in a professional environment. Some recipients of feedback would prefer to receive a "nicer" feedback, while others prefer (or only respond to) direct feedback.
For the giver of feedback, when possible, either showing the intent to help others succeed in the future, simply showing support, or making the best out of a bad situation results in the best delivery of the bad news. Just my opinion of course.