There isn't enough information in the Accident Report to really determine what happened. However if the limited information available is accurate it appears this may have been a flutter event. I once heard an aircraft flutter and a sound a bit like a misfiring engine is a reasonable description. The witness statements that the aircraft had commenced a right turn do not fit the overloaded outboard section of wing failing in the downward mode scenario. If that scenario had occurred the right wing would be the broken one. Turning right would speed up the left wing and perhaps that was the straw that broke the camels back. C210's don't have a great flutter margin but it is of no concern providing it is flown inside the design envelope. There is an aileron beef up mod available. This was developed when people started playing with much more powerful engine installations such as turbines.
Cheers RA