Hello Michael.

I repeated the test and I've found maybe a strange behavior, but I don't know if I'm doing something wrong or not.
It's something I can't figure out.

Please check this brief video : http://take.ms/nuPqd

This is a textual explanation, but it's better to check the video.

1) I created a box 50x50x50 with a circular fillet of 10
2) I tried to "offeset" one single surface (without separate from the body)
3) AS YOU CAN SEE THE FILLET DOESN'T WORK

4) This time I created the same box 50x50x50 but with a g2 fillet of 10
5) I tried to "offeset" one single surface (without separate from the body)
6) AS YOU CAN SEE IT WORKS!

I stay tuned. Thanks.