Glad to see facebitter is out of aviation, hopefully he stays that way.
Not a turbine engine expert, but do have some engineering background relevant to turbines in general (big industrial units as well as aircraft). Like JNB, my gut feel is that I would actually expect to see significantly more hot section damage if the power turbine came apart at TO power. At that kind of rpm, the imbalance should cause the entire turbine assembly to rip itself out of the hot section and disintegrate. But like I said, not an expert on PT-6's by any means.