Think you may perhaps have your N1/N2 confused. N1 is the compressor spool and N2 is the power output spool (what drives the prop). N2 will be rotating if wind is driving the prop, N1 maybe/maybe not depending on airflow through the engine. The accessories gear box (and oil pump) are driven by the N1.
A feathered engine (on King Air at least) will slowly rotate, so doubt anything detremental happening, but check with your maintenance people.
http://vid101.photobucket.com/albums...psd6911dfd.mp4
http://www.pwc.ca/files/en/Know_your_PT6A.pdf