The whole incident is a tragedy, an instructor trying to do what he thought was the right thing, and hindsight demonstrating that the actions may have inadvertantly increased the student's workload. A student who also probably thought the formation would make it easier, found himself in a tough place.
Few R22 PPL's would fancy handling a subtle carb ice engine failure (if, as the report suggests, that was the likely scenario), just hope the real world pans out as well as the training.
The instructor will no doubt find his decisions hard to live with irrespective of the report's findings, and the pilot's family gets no definitive answers.
BW