As I mentioned in an earlier post, the King Air 200/300 have a special condition associated with their certification, which acknowledges very high yaw angles which can be achieved. Yaw angles approaching 40 degrees are possible, in more or less level flight, and the effect is more pronounced with the nose gear extended. I can't help thinking this could have been a factor. I have explored these high yaw angles while flight testing a modified 200, and the characteristic is real. I was warned (and required) to test for it. However, if a pilot were unaware of this characteristic, and blundered into it, it would be really surprising. That coupled with an unintended power lever roll back (also a known event in King Airs, if the friction is not set), and single pilot, so task saturation, would create these circumstances...
The feathering and autofeather of the PT6 is very smooth and effective. There are few "power" effects during feathering, it just winds down and feathers. Unfeather, on the other hand, must be handled very gently!