This is entirely speculation and certainly not confirmed -- but it is quite possible that the same instructors who were training him also sent him off alone to assist with the other OW group.
PADI teaches to always dive with a buddy... DM's or DMC's have nothing in their course materials for "solo diving". However I don't think I know of any DM's that assist with classes Rescue and O/W specifically where they aren't needed to solo dive. I know I have more times than I remember. I don't think its so much of a training issue on solo diving since everyone is taught how to safely ascend. I think in this case the individual has some outside factor that made him uncomfortable and clouded his thinking to the point where there was panic. Being a DM isn't for everyone and not everyone that wants to be a DM is ready at 60 dives either. The instructor has some responsibility in any training dive even to DMC's/DM's to express concerns if there are any.