I have 4 polystone statues and I will never buy one ever again, three are perfect the other I should have known better. Plus always worrying if their is a earthquake it's happened twice to me.
What they do is pour into a mold and when it drys it's like a porcelain statue, then they paint it.
From looking at the pics I'm pretty dam sure every part it is polystone and that no part is pvc. That's why they cost about double or more but the downsides is that they are more fragile, weigh a ton, and the paint they use is usually flat and non glossy.
Now are you asking is it castoff-able out of the box I would say no. If you want to modify it you probably could but it would be a pain and not that easy since when you try to remove any part it will chip or break and unless you want to add sculpting clay and repaint.
Go here:
http://www.nekomagic.com/?p=23694
It looks like the original garage kit that you make and paint yourself can be made cast off no surprise resin is more forgiving but not the completed polystone figure.