Interesting. I've never tried doing this before.
It looks like if the handle is directly under the world it'll update its translation to match the new location of the end effector. If it's parented to something other than world, it won't update translation. Instead, it'll rotate the parent bones to reach the new end effector. I have no idea why it would behave differently like that.
In general, I like to make sure that I've got the bones in the right place before I set up IK. If I need to adjust anything, I'll delete the IK and recreate it after moving joints. That way I can make sure I've got the joint orientation I want.