I totally agree with fluffy. I have tried polypiling with good gear vs balsa sticks and not noticed any difference in the quality of the morphed goods. Thats why I said "what a waste..."
However if polymorphing does change only the chest then that would make it one of the better ways to access the contents.
I did some testing. First of all, I was
wrong - I don't really know why I got the impression that polymorph is affected by item quality.
But second of all, polymorphing a chest does not
alter the contexts, and spills them, explaining why I got high-quality stuff when polymorphing that chest!