I suspect that the sensor issue/5% tq split will have had very little to do with the accident. Find me any 20+ year old turboprop with perfectly matched engines and I'll be surprised. Indeed from experience on TPE J31s I doubt it would be noticeable. Remember we're talking old machines who have lived a hard life here. Even two matched engines could be confused as being not matched due to trimming for bad rigging in the controls, an airframe which isn't perfectly true etc etc.
My concerns are, as alluded to by some folks above:
1. They shouldn't have been there in the first place. Period.
2. The mention of being below flight idle in the interim report. If they went into beta, which would have dropped them from the sky like a brick, And may well have rolled them, They stood no chance of recovery from their self induced error.
3. The captain operating the power levers whilst the FO flew. Ridiculous. Flies in the face of all good practice. If the FO was struggling the skipper should have been handling, especially in the conditions.
Sadly I feel the whole thing still comes down to gross pilot error. The engine issue is just a red herring, which the authority understandably have to report in their thorough investigation.