I don't care if it's "correct" or not to turn shadows on for an IBL, I'm going to do it if in doing so I get the effect I want. :-)"

That's the mark of a canny artist. :)

I'm also annoyed by these return-to-default things. 

There's no reason for them; all the changes you mentioned are written in the PZ3. 
But Poser decides on its own that it doesn't really need to read everything in the PZ3.
 
It's like leaving your carpentry tools laid out on the workbench at night, then finding
that the janitor has disassembled your jigs and reset all the calipers and
micrometers to 0, because they look nicer that way.

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