Hi ,
There are a couple of issues.
In your post from Fusion there is no cutter comp. Hence no G41/G42 Dx. Its "In computer" by default. That is , its offsetting it by the dia of the cutter and generating a post. There is a drop down to select how you want to do it, in the passes tab.
My problem is , then Linuxcnc doesn't like the post from Fusion, something about the format. I will have to write down the exact error.