The Jab engine may well have been overheated - I don't think anybody is disputing that. The dispute was about whether the pilots took off with an indication of that, and whether the aeroplane was operated outside the operating handbook. Neither of those things are the case.
If there is some special technique required to fly these aeroplanes, where is it written in the POH? How else would pilots be educated?
It seems fairly clear that the aeroplane isn't designed for heavy training use. Two engine failures in a week with no prior indications is an abysmal record for any aircraft type. Think they'd be better off leaving recreational aeroplanes where they belong before someone gets killed.